Please help me with these questions.

1.

A company that produces cell phones has a cost function of C = 17:22 3069: + 19475, where C is the cost in dollars and a: is the number of cell phones produced (in thousands). How many units of cell phone (in thousands) minimizes the cost function? x = :] thousand phones produced will minimize C \fA stone is thrown straight up from the edge of a roof, 600 feet above the ground, at a speed of 18 feet per second. A. Remembering that the acceleration due to gravity is -32 feet per second squared, how high is the stone B. At what time does the stone hit the ground? C. What is the velocity of the stone when it hits the ground? :] n IN Given Rn = : [ ( 6 + 1 2 ) " - 3 5 6 , express the limit as n -> oo as a definite n n b integral, that is provide a, b and f(a) in the expression f(x)dx. a a = b f (ac ) =