diff --git a/src/calculateRentalCost.js b/src/calculateRentalCost.js
index 1e3a27d11..bed4aee6f 100644
--- a/src/calculateRentalCost.js
+++ b/src/calculateRentalCost.js
@@ -4,7 +4,26 @@
  * @return {number}
  */
 function calculateRentalCost(days) {
-  // write code here
+  const PRICE_OF_RENT = 40;
+  let totalCost = days * PRICE_OF_RENT;
+  const SHORT_TERM = 3;
+  const SMALL_DISCOUNT = 20;
+  const LONG_TERM = 7;
+  const BIG_DISCOUNT = 50;
+
+  if (days < SHORT_TERM) {
+    return totalCost;
+  }
+
+  if (days < LONG_TERM) {
+    totalCost = totalCost - SMALL_DISCOUNT;
+
+    return totalCost;
+  }
+
+  totalCost = totalCost - BIG_DISCOUNT;
+
+  return totalCost;
 }
 
 module.exports = calculateRentalCost;