4) The volume of a cube is increasing at the rate of 12 in³/min . How fast is the surface area increasing, in square inches per minute, when the length of an edge is 20 in?
(A) 1
(B) 6/5
(C) 4/3
(D) 12/5
5) At which of the five points on the graph in the figure above is dy/dx > 0 and d²y/dx² > 0?
(A) A
(B) B
(C) C
(D) D
6) What is the area of the largest rectangle that has its base on the x-axis and its other two vertices on the parabola y = 6 - x² ?
(A) 8√2
(B) 6√2
(C) 4√3
(D) 3√2
7) If y = 1/√x - √x, what is the maximum value of the product of xy?
(A) 1/9
(B) √3/9
(C) 2√3/9
(D) 2/3