diff --git a/src/calculateRentalCost.js b/src/calculateRentalCost.js
index 1e3a27d11..3813a1eff 100644
--- a/src/calculateRentalCost.js
+++ b/src/calculateRentalCost.js
@@ -4,7 +4,17 @@
  * @return {number}
  */
 function calculateRentalCost(days) {
-  // write code here
+  const total = days * 40;
+
+  if (days >= 7) {
+    return total - 50;
+  }
+
+  if (days >= 3) {
+    return total - 20;
+  }
+
+  return total;
 }
 
 module.exports = calculateRentalCost;