diff --git a/week3/Cargo.lock b/week3/Cargo.lock
index d04310f..2942eb8 100644
--- a/week3/Cargo.lock
+++ b/week3/Cargo.lock
@@ -2,6 +2,74 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "getrandom"
+version = "0.2.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c05aeb6a22b8f62540c194aac980f2115af067bfe15a0734d7277a768d396b31"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.139"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "201de327520df007757c1f0adce6e827fe8562fbc28bfd9c15571c66ca1f5f79"
+
+[[package]]
+name = "ppv-lite86"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b40af805b3121feab8a3c29f04d8ad262fa8e0561883e7653e024ae4479e6de"
+
+[[package]]
+name = "rand"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
+dependencies = [
+ "libc",
+ "rand_chacha",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "wasi"
+version = "0.11.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
+
 [[package]]
 name = "week3"
 version = "0.1.0"
+dependencies = [
+ "rand",
+]
diff --git a/week3/Cargo.toml b/week3/Cargo.toml
index 855ff21..e5a0c5a 100644
--- a/week3/Cargo.toml
+++ b/week3/Cargo.toml
@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+rand = "0.8.5"
diff --git a/week3/src/lib.rs b/week3/src/lib.rs
index 8b13789..4e92f1b 100644
--- a/week3/src/lib.rs
+++ b/week3/src/lib.rs
@@ -1 +1,85 @@
+use rand::prelude::*;
+use std::f64::consts::PI;
 
+#[derive(Debug)]
+pub enum Shape {
+    Circle(f64),
+    Square(isize),
+    Rectangle(isize, isize),
+}
+
+pub fn area(shape: &Shape) -> f64 {
+    match shape {
+        Shape::Circle(radius) => radius * radius * PI,
+        Shape::Square(length) => (length * length) as f64,
+        Shape::Rectangle(width, height) => (height * width) as f64,
+    }
+}
+
+pub fn random_shape() -> Shape {
+    let mut rng = rand::thread_rng();
+    let random_number: isize = rng.gen_range(0..2);
+
+    match random_number {
+        0 => Shape::Circle(rng.gen()),
+        1 => Shape::Rectangle(rng.gen(), rng.gen()),
+        _ => Shape::Square(rng.gen()),
+    }
+}
+
+pub fn circle_area(shape: &Shape) -> Option<f64> {
+    if let Shape::Circle(shape) = shape {
+        Some(area(&Shape::Circle(*shape)))
+    } else {
+        None
+    }
+}
+
+#[cfg(test)]
+mod test_shape_areas {
+    use super::*;
+
+    #[test]
+    fn gets_area_of_circle() {
+        const RADIUS: f64 = 1.0;
+        const ANSWER: f64 = 3.141592653589793;
+
+        let circle = Shape::Circle(RADIUS);
+
+        assert_eq!(ANSWER, area(&circle));
+    }
+    #[test]
+    fn gets_area_of_rectangle() {
+        const WIDTH: isize = 100;
+        const HEIGHT: isize = 20;
+        const ANSWER: f64 = 2000.0 as f64;
+        let rectangle = Shape::Rectangle(WIDTH, HEIGHT);
+
+        assert_eq!(ANSWER, area(&rectangle));
+    }
+    #[test]
+    fn gets_area_of_square() {
+        const LENGTH: isize = 100;
+        const ANSWER: f64 = 10000.0 as f64;
+        let square = Shape::Square(LENGTH);
+
+        assert_eq!(ANSWER, area(&square));
+    }
+    #[test]
+    fn gets_circle_area() {
+        const RADIUS: f64 = 1.0;
+        const ANSWER: Option<f64> = Some(3.141592653589793);
+
+        let circle = Shape::Circle(RADIUS);
+
+        assert_eq!(ANSWER, circle_area(&circle));
+    }
+    #[test]
+    fn gets_circle_area_else() {
+        const LENGTH: isize = 100;
+
+        let square = Shape::Square(LENGTH);
+
+        assert_eq!(None, circle_area(&square));
+    }
+}
diff --git a/week3/src/main.rs b/week3/src/main.rs
new file mode 100644
index 0000000..361c417
--- /dev/null
+++ b/week3/src/main.rs
@@ -0,0 +1,6 @@
+use week3::random_shape;
+
+fn main() {
+    let shape = random_shape();
+    println!("{:?}", shape);
+}