Plz solve

D Question 9 4 pts Given the function f (z) - - 4x2 + 5x, find the open interval(s) where f is concave down. (4/3, infinity) [4/3.infinity) (-Infinity, 4/3] (-infinity, 4/3) D Question 10 4 pts From a thin piece of cardboard 20in by 20in, square comers are cut out so that the sides can be folded up to make a box. What dimensions will yield a box of maximum volume? 6.7 by 6.7 by 6.7 in 13,3 by 13.3 by 3.3 in. 13.3 by 13,3 by 6.7 In 10 by 10 by 5 in D Question 11 4 pts A carpenter is building a rectangular room with a fixed perimeter of 140 ft. What the dimensions of the largest room that can be built? What is its area? 70 by 70 ft; 4900 ft^2 14 by 126 ft; 1764 ft^2 35 by 105 ft; 3675 ft2 35 by 35 ft: 1225 ft^2 D Question 12 4 pts We need to enclose a field with a fence. We have 500 feet of fencing material and a building is on one side of the field and so we won't need any fencing, Determine the dimensions of the field that will enclose the largest area. x 200, y=100 x-150, y-200 x 250, y=125 x-125. y =100 D Question 13 4 pts Using the following properties, select a possible graph of y. y' >0 (-infinity,-2)and (2,infinity) y 0 10, infinity) (-infinity.0) Goes through the points: (-2,11). (0,-5), and (2,-21) A D) PB DA BD C