This is a 2 part problem. First, we need to find the area of each side, then add them together. (the question isn't asking for volume).
1) The board has six sides(top, bottom, four sides). the top + bottom are 4 by 24 in, the short sides are 2 by 4 inches, and the long sides are 2 by 24 inches. After multiplying, this gives us 96 sq in + 96 sq in for the top and bottom, 8 sq in and 8 sq in for the short sides, and 48 sq in + 48 sq in for the long sides.
2) If we add all of these together, we get 96 + 96 + 8 + 8 + 48 + 48 = 192 + 16 + 96 = 304 sq inches, which is the total surface area.