Harlan Grove wrote...
....
=AVERAGE(IF(LEFT(A2:A640,2)="TU",1,LEFT(A2:A640,5 )="ANA36"),B2:B640)
....

Make that

=AVERAGE(IF(IF(LEFT(A2:A640,2)="TU",1,LEFT(A2:A640 ,5)="ANA36"),B2:B640))