I have a problem with summing a lookup function

My data looks like this:

A1: text B1: time C1: time D1: time E1: time

A1 = could be any of 8 different sets of two letter initials of counselor
B1 = time arrived
C1 = time seen
D1 = time departed
E1 = average wait time

I have a table from A1:D40. I want to query this table, by counselor , and
return the average wait time for each counselor. Exampe: "DF" shows up three
times and has the wait times of 3 min, 6 min and 4 min then the return answer
would be 4 min 20 sec. (3+6+4)/3 = 4'20"

Any help? Maybe the lookup function is not my answer. Thanks in advance.

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LAMP