VB 2010 Assignment

I've been told this type of post has been answered before but Ive searched and couldn't find anything.
Can anyone help me out or point me in the direction of a post that could. Thanks

Read a text file containing a single student's grades. Each line simply contains a letter grade. You can assume that each course is 3 credits
Task: Compute the student's GPA
Grade table is as follows
A 4.0
A- 3.67
B+ 3.33
B 3.0
B- 2.67
C+ 2.33
C 2.0
C- 1.67
D 1.0
F 0

GPA is computed by obtaining the total quality points and dividing by total credits
Quality Points are calculated by multiplying the points for the grade by the number of credits

the output should read "student's GPa is xx.xx" usising two decimal places
The GUI is a Button and an output label

txtfile

A

A-

C

D

C-

B