The surface area of a box is computed as follows:
area = 2*length*width + 2*length*height + 2*height*width
Replacing with length = 12, width = 4, and height = 3,
area = 2*12*4 + 2*12*3 + 2*3*4
area = 96 + 72 + 24
area = 192 sq. ft
The volume of a box is computed as follows:
volume = length*width*height