The answer is " 768 square feet. ".
Total surface area of a triangular prism = width x height +(sum of sides + width) x length and here;
width = 10
height = 12
sides = 13
length = 18
= (10 x 12) + (13 + 13 + 10) x 18
= 120 + (36 x 18)
= 120 + 648
= 768 square feet.
