How To Create Form That Calculates QB Ratings

I am creating a form that calculates QB Ratings but its not coming out right. The formula is found here

My code:
Dim a, b, c, d As Integer
a = (Comp.Text / Att.Text * 100 - 30) / 20
b = (Yards.Text / Att.Text - 3) * 0.25
c = Tds.Text / Att.Text * 20
d = 2.375 - (Int.Text / Att.Text * 25)
Rating.Text = "QB Rating:" & ((a + b + c + d) / 6) * 100

Number set 1:
22 complete
36 Attempt
2 touchdowns
0 Interceptions
229 yards
It should come out 98.0 but comes out 100

Number set 2:
16 complete
37 Attempt
0 touchdowns
3 Interceptions
205 yards
It should come out 27.4 but comes out 33.3