FIND THE FOLLOWING USING THE GIVEN TRIANGLE...PLEASE HELP ME SUCK AT MATH...SOS!!! ASAP!!!!

perimeter = 20 +20 +24 = 64 feet
area = 12^2 + x^2 = 20^2
144 + x^2 = 400
x^2 = 256
x = sqrt(256) = 16 feet
area = 1/2 x 16 x 24 = 192 square feet
cost = 192 x $2 = $384