Sum if with multiple conditions

[JaredL]

I have a spreadsheet containing a sum if

i want to test TWO conditions on the sum if

if there is a simple way to do this?

IE. if one column contains "Yes" and another column contains a specified name "Mary" then add up mary's test scores which are located in another column

help??

[martindwilson]

=sumproduct(--(a1:a100="mary"),--(b1:b100="yes"),(c1:c100))