Area of all 5 FACES = (Height • Width • Number of Sides)
(Height • Width • Number of Sides) = 20 * 8 * 5 = 800 = Area of all 5 FACES
Area of the 2 BASES = number of sides * side length * apothem
Area of the 2 BASES = 5 * 8 * 5.5 = 220
TOTAL Area = 800 + 220
TOTAL Area = 1,020
Sources
1728.com/volprism.htm
1728.com/polygon.htm