5 x 9 = 45
thats the area of one of the sides, and since the opposite side is identical, it's also 45
so mulitply 45 by 2, you get 90
then do 5 x 10, you get 50
multiply that by 2 and you get 100
finally, 9 x 10 = 90
90 x 2 is 180
so now add the final numbers
90 + 100 + 180 is 370.
the surface area is 370 square inches