diff --git a/src/calculateRentalCost.js b/src/calculateRentalCost.js
index 1e3a27d11..d14a87ed2 100644
--- a/src/calculateRentalCost.js
+++ b/src/calculateRentalCost.js
@@ -4,7 +4,23 @@
  * @return {number}
  */
 function calculateRentalCost(days) {
-  // write code here
+  const LONG_TERM = 7;
+  const LONG_TERM_DISCOUNT = 50;
+  const SHORT_TERM = 3;
+  const SHORT_TERM_DISCOUNT = 20;
+  const RENT_A_DAY = 40;
+
+  if (days < SHORT_TERM) {
+    return days * RENT_A_DAY;
+  }
+
+  if (days < LONG_TERM) {
+    return days * RENT_A_DAY - SHORT_TERM_DISCOUNT;
+  }
+
+  if (days >= LONG_TERM) {
+    return days * RENT_A_DAY - LONG_TERM_DISCOUNT;
+  }
 }
 
 module.exports = calculateRentalCost;