Carly's Clippers total revenue #9 coding question

Hi, I’m working on the below problem:

Why doesn’t my code result in the correct answer to number 9?

for last in last_week:
total_revenue += price*last

This the correct code:
for i in range (len(hairstyles)):
total_revenue += prices[i] * last_week[i]

There’s no way for the computer to know which price you’re referring to [as price] in that loop.

You could fix that by using zip or by iterating using the indices.