diff --git a/Chapter09/Cargo.toml b/Chapter09/Cargo.toml
index 39b5f1b..6af6578 100644
--- a/Chapter09/Cargo.toml
+++ b/Chapter09/Cargo.toml
@@ -50,3 +50,11 @@ path = "performance_polynomial1.rs"
 [[bin]]
 name = "performance_polynomial2"
 path = "performance_polynomial2.rs"
+
+[[bin]]
+name = "performance_polynomial3"
+path = "performance_polynomial3.rs"
+
+[[bin]]
+name = "performance_polynomial4"
+path = "performance_polynomial4.rs"
diff --git a/Chapter09/performance_polynomial3.rs b/Chapter09/performance_polynomial3.rs
new file mode 100644
index 0000000..40dedfc
--- /dev/null
+++ b/Chapter09/performance_polynomial3.rs
@@ -0,0 +1,25 @@
+fn a(n: u64) {
+   //Is this O(n)?
+   for _ in 0..n {
+      b(n)
+   }
+}
+
+fn b(n: u64) {
+   //Is this O(n)?
+   for _ in 0..n {
+      c(n)
+   }
+}
+
+fn c(n: u64) {
+   //This is O(n)?
+   for _ in 0..n {
+      let _ = 1 + 1;
+   }
+}
+
+fn main() {
+   //What time complexity is this?
+   a(1000)
+}
diff --git a/Chapter09/performance_polynomial4.rs b/Chapter09/performance_polynomial4.rs
new file mode 100644
index 0000000..f79c691
--- /dev/null
+++ b/Chapter09/performance_polynomial4.rs
@@ -0,0 +1,2 @@
+fn main() {
+}