The area of each book is 63 in2. the height of the stack is 15.75 inches. what is the volume of the stack of books? a) 337.85 in3 b) 665.21 in3 c) 850.15 in3 d) 992.25 in3

The function a represents the cost of manufacturing product a, in hundreds of dollars, and the function b represents the cost of manufacturing product b, in hundreds of dollars. a(t) = 5t + 2 b(t) = 7t - 2t +4 find the expression that describes the total cost of manufacturing both products, a(t) + b(t). a. 7t^2 - 7t + 2 b. 7t^2 + 3 +6 c. 7t^2 + 7t - 6 d. 7t^2 - 3t + 6