The following results in a #VALUE error, even when array-entered, which should not be necessary:
=SUMPRODUCT(C10:C13,VLOOKUP(B10:B13,A4:B6,2,0))
The intended interpretation is:
C10*VLOOKUP(B10,A4:B6,2,0) + C11*VLOOKUP(B11,A4:B6,2,0) + ....
The following work-around does not produce the...