
1 cell array formula in J2:
=SUM((B2:B20="A")*C2:C20*ISERROR(MATCH(A2:A20,IF(A2:A20&B2:B20=A2:A20&"C",A2:A20),0)))
, , I2, . "_S1", "_S2" "_S3" .
I2 -
=SUMPRODUCT(_S1,_S3)
_S1 -
=(B2:B20="A")*C2:C20
"" .
_S2 -
=IF(A2:A20&B2:B20=A2:A20&"C",A2:A20)
, "C" FALSE.
_S3 -
=ISERROR(MATCH(A2:A20,_S2,0))*1
A "C-" _S2. , 0, 1.