Winston is creating a rectangular piece of 8-bit art using squares that are x pixels wide. The length of the rectangular piece, in pixels, is represented by the function l(x) = x + 24, and the width of the rectangular piece is represented by w(x) = x + 16. Write the standard form of the function which describes the total area of the rectangular piece, a(x), in terms of x, the side length of each square pixel.