Finding the sum of cells from column A that meet criteria in column B

I am trying to calculate the sum of revenue from events that used a certificate instead of paying for the package.

excell help.JPG

In the image above, the Q column is for comments. Each event that used the certificate will contain the letters "cert". The conditional formatting marks them yellow.
In Column AB, I have the revenue that we received from all the events. The events whose revenue is lower than the package cost is marked yellow with conditional formatting.
I want to take a sum of only those event's revenues.

I tried the following formula in the red-circled cell, but it did not work:

=SUM(AB2:AB488(COUNTIF(Q2:Q488,{"*cert*"})))

Which part is wrong?

I have also tried this: =SUMIF($Q$2:$Q$488,'*cert*',$AB$2:$AB$488)

welcome to the forum. almost there:
=SUMIF($Q$2:$Q$488,"*cert*",$AB$2:$AB$488)

or 1 wildcard lesser if the words all START from cert:
=SUMIF($Q$2:$Q$488,"cert*",$AB$2:$AB$488)

I was trying to see the difference btw OP and benishiryo.

OP =SUMIF($Q$2:$Q$488,'*cert*',$AB$2:$AB$488)
Ben=SUMIF($Q$2:$Q$488,"*cert*",$AB$2:$AB$488)

Leanna, note your use of '*cert*' compared to Ben's. Your profile says you are in USA (?), therefor you need to use " not '

I was actually referring to your use of ' compared to the corrected usage of "