The solid consists of a square based pyramid and a cube.
The surface area of the solid would be the sum of the surface of the square base pyramid and the cube. The pyramid has four triangular faces. The height of each triangular face is 15ft while the base is also 15ft. Recall,
Area of traingle = 1/2 x base x height
Area of each triangular face = 1/2 x 15 x 15 = 112.5
Area of 4 triangular faces = 4 * 112.5 = 450 ft^2
The cube has 6 faces but only 5 is required.
Area of each face = 15 x 15 = 225
Area of 5 faces = 225 x 5 = 1125
Thus,
Surface area of the figure = 450 + 1125 = 1575 ft^3
The volume of the solid would be the sum of the volume of square base pyramid and the cube. The formula for determining the volume of a square base prism is
Volume = 1/3 x base area x height
base area = 15 x 15 = 225
Volume = 1/3 x 225 x 15 = 1125
The formula for finding the volume of a cube is
Volume = s^3
where s is the length of each side
Volume = 15^3 = 3375
Thus,
Volume of the figure = 1125 + 3375 = 4500 ft^3