if you'd used the logicals TRUE/FALSE instead of yes/no then the array counter could simply be
=SUM(B2:B5*C2:C5)
NB entered as an array with ctrl-sh-enter

using yes/no the array formula needed is
=SUM((B2:B5="Yes")*(C2:C5="Yes"))
or
=SUM((TRIM(B2:B5)="Yes")*(TRIM(C2:C5)="Yes"))
if your entries may contain aberrant spaces