# javascript – How to calculate the total cost when the unit price changes in steps?

## Question:

The user enters the number of emails and receives the total cost of the mailing. There is an array of number of `post` letters and an array of prices for sending one letter from these `prescurant` ranges

``````var post       = [1000, 3000, 5000, 10000, 20000];
var prescurant = [0,    0.08, 0.07, 0.06,  0.05, 0.04];
``````
• for the first 1000 letters, the user will give 0 rubles each;
• for letters from 1001 to 3000, he will give 0.08 rubles. for the letter;
• from 3001 to 5000 – 0.07 rubles each;
• etc.
• each letter over 20,000 costs 0.04 rubles.

How to calculate the total cost when the unit price changes in steps and these thresholds are set?

Tried like this:

``````var val=2000//введеные пользователем кол-во писем
for(i=0;i<post.length;i++){
for(j=0;j<prescurant.length;j++){
otv=(post[i]-post[i+1])*prescurant[j]
}
}
\$("#otv").html(otv)
``````

``````var post=[1000,3000,5000,10000,20000],prescurant=[0,0.08,0.07,0.06,0.05,0.04],val=5001;