Asquare pyramid has a base with side lengths each measuring 40 inches. the pyramid is 21 inches tall, with a slant height of 29 inches. what is the surface area of the pyramid? 3,280 inches 3,280 square inches 3,920 inches 3,920 square inches

Check the picture below.

since the slant height of the pyramid is 29, that'd be the altitude or height of a triangular face, whose base is 40.

we can simply get the area of the the base, it's just a 40x40, and the area of all 4 triangular faces and sum them up, and that's the surface area of the pyramid.