We could approach the stereo receiver to a rectangular prism, that has the formula of surface area (A):
[tex]A=2ab+2bc+2ac[/tex]
As the dimensions are given: a = 18", b = 16", c = 9"; then we just have to replace these values in the formula:
[tex]A=2(18)(16)+2(16)(9)+2(18)(9)[/tex]
Simplifying:
[tex]A=576+288+324[/tex]
[tex]A=1188[/tex]
Answer: 1188 in²
