The height of a triangular truss is 5 ft less than the base. The amount of drywall needed to cover the triangular area is 84 ft. Find the base and height of the triangle to the nearest tenth of a foot. Select one: a. base-15.9 ft; height - 10.9 ft Ob. base 21 ft; height - 16 ft Oc. base- 12 ft; height = 7 ft d. base 15.7 ft; height -10.7 ft