Prevent unlogical calculations

src/interestCalculator.c

@@ -17,6 +17,9 @@ void troubleshoot(int errorCode){
         case 3:
             printf("Invalid option. Aborting.");
             break;
+        case 4:
+            printf("Your goal cannot be smaller than your principal funds. Aborting.");
+            break;
     }
 }
 
@@ -24,16 +27,21 @@ void askForSavingGoal(float principalAmount, float accInterestPerYear){
     char c;
     float goal;
     float timeForGoal;
-    printf("\nWould you like to set a saving goal?");
+    printf("\nWould you like to set a saving goal? [y] yes [any] no");
     scanf(" %c",&c);
     
     if(c=='y'||c=='Y'){
         printf("\nPlease enter your goal amount in €:");
         scanf("%f",&goal);
+        if(goal>=principalAmount){
             timeForGoal=(goal-principalAmount)/accInterestPerYear;
-        printf("In %.1f years you will reach your goal of %f.\n", timeForGoal, goal);
+            printf("\nIn %.1f years you will reach your goal of %f.\n", timeForGoal, goal);
         }else{
-        //error
+            troubleshoot(4);
+            return;
+        }
+    }else{
+        return;
     }
 
 }