I want to calculate the average of scores achieved by a guy.

for e.g:
A B C D E
1 2 3 4
smith 98 65 98 96
donald 97 94 92 93
alex 91 90 89 97
ronald 91 94 95 97
jose 94 95 92 90
brad 94 91 95 94
donald 98 65 98 96
brad 97 94 92 93
jose 91 90 89 97
alex 91 94 95 97
davis 94 95 92 90
smith 94 91 95 94

average of Scores achieved by alex(if his name is there in column A)

lets say i want the answer in B17.......

What formulae should I derive to calculate this?