yogi_Sum Up Entries In Column B For Entries In Column A That Match List of Entries In Range C2 to C

                                          Google Spreadsheet   Post  #1463
Yogi Anand, D.Eng, P.E.      ANAND Enterprises LLC -- Rochester Hills MI     www.energyefficientbuild.com.   Jan-01-2014
post by CoryT87(http://productforums.google.com/forum/?zx=f1190urkz7zs#!category-topic/docs/spreadsheets/-UrLFYhgeVM)
'=sumif
how would i use the =sumif formula with 2 words in it instead of just one?
---
here's an example of what im wanting to do:

Column A          Column B                     Column C

aa                          2                             aa

aa                          5                             ad

ab                          14                           

ad                          0 

ab                          4

ab                          19

ab                          25

i want to do a =sumif formula like this: =sumif(A:A,"",B:B) where it adds the sum of both "aa" and "ab" because "aa" & "ab" both are the same type and the formula is inputted into column c. if that doesnt make any sense at all please let me know.

-----------------------------------------------------------------------

based on my understanding that you want to sum up amounts in column B for entries in column A that match items listed in C2:C ...

I present the solution to a bit more generalized problem as follows