diff --git a/trade_checker.js b/trade_checker.js
index ef2d5a9..9406ce2 100644
--- a/trade_checker.js
+++ b/trade_checker.js
@@ -50,7 +50,7 @@ class TradeChecker {
             final_amount += key_count * this.MONTH
 
         if(metal_count >= this.prices_map["week"])
-            final_amount += (metal_count / self.prices_map["week"]) * this.WEEK;
+            final_amount += (metal_count / this.prices_map["week"]) * this.WEEK;
         else if(metal_count >= this.prices_map["day"])
             final_amount += (metal_count / this.prices_map["day"]) * this.DAY;