28a. Top Area = length x width
A = (4a - 4)(a + 1)
A = 4a² + 4a - 4a - 4
A = 4a² - 4
28b. Front Area = length x height
A = (4a - 4)(a + 3)
A = 4a² + 12a - 4a - 12
A = 4a² + 8a - 12
28c. V = l x w x h
V = (4a - 4)(a + 1)(a + 3)
V = (4a² - 4)(a + 3)
V = 4a³ + 12a² - 4a - 12