A triangular pyramid has a base shaped like an equilateral triangle. The legs of the equilateral triangle are all 11 inches long, and the height of the equilateral triangle is 9.5 inches. The pyramid's slant height is 12 inches. What is its surface area?
help
ful formula: Surface Area = (1/2) * Base Area * Slant Height
Answer: 567.5 in^2