need help calculating based on a given grade.

[nasser4life]

A1 = $1, B1 is a grade from 6-9, C1 is a total.

6 = 50%, 7= 100%, 8= 150%, 9=200%
or 6=1.5, 7=2, 8=2.5, 9=3

example if a grade of 8 was given, 100% of $1 would be added to the based which is A1 making C1=$2

I wanted a formula for C1 that would lookup the grade in B1 and then multiple the grade percentage by A1.

I want to be able to change grades freely so the formula should be in C1. any help would be appreciated.