I simply can't figure this out...

I have multiple locations that I need to find specific criteria and sum:

A B C
D
LOCATION DESCRIPTION1 DESCRIPTION2 AMOUNT
------------- ----------------- ----------------- ------------
1 MC blank
$50
1 PURCHASE MC $20
1 AMEX blank
$10
5 AMEX blank $25
7 PURCHASE VISA $75
7 VISA blank
$100

For example:
I want to find to total $ for location 1 with description of MC in either
column B or C. So this example would total $70.
Help?
Thank you!!!
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-A