Hi Anyone

I have the following on a spreadshhet


Col A Col B Col C
Duncan cat1 10
Duncan cat2 30
Paul cat 3 5
Craig cat 1 60
Paul cat 2 30
Craig cat3 20
Duncan cat1 23

I would like to know the formula to add column C using column A as my first
criteria then column B as my second criteria to achieve the following result

Duncan Cat 1 = 33
Duncan Cat 2 = 30
Paul Cat 2 = 30
And so on
All help is greatly appreciated