Please help with questions below

Solve the problem. 1) It is estimated that the cost of constructing an office building that is n floors high is 1) C(n) = 3n2 + 350n + 700 thousand dollars. How many floors should the building have to minimize the average cost per floor? (Remember that your answer should be a whole number.) A) 16 floors B) 15 floors C) 17 floors D) 18 floors Specify the intervals on which the derivative of the given function is positive and those on which it is negative. 2) Solve the problem. 3) The cost of producing x units of a commodity per week is C(x) =0.3x3 - 9x2 + 34x +500 Find all values of x where C"(x) = 0. How are these levels of production related to the graph of the marginal cost