Arain gutter is to be constructed of aluminum sheets 12 inches wide. after marking off a length of 4 inches from each edge, this length is bent up at an angle θ. the area a of the opening may be expressed as the function: a(θ) = 16 sin θ • (cos θ + 1). if θ = 90°, what is the area of the opening? a. 21.8 in^2 b. 16.0 in^2 c. 7.9 in^2 d. 1.0 in^2