I have the following table, and would like to sum the value of C with the
criteria A=Production, and B=External. I have so far
SUMIF(A:A,"Production",C:C)...but can't work out how to add AND B:B,"
External". In this case the return for my request will be C1 + C5

A B C
Production External £28,240
Design External £71,908
Production InterGroup £159,070
Design External £3,600
Production External £327,700

Thanks for any help offered!