I need help with 5 and 6

4. Determine the open intervals where the function is concave upward and the intervals where the function is concave downward. Find the inflection point(s) of the function. f (x) = x6 - 27 7* -15x + 20 5. Lucky Dog Daycare will be enclosing a 900 square feet outdoor area. One side will be formed by the external wall of their building, two sides will be constructed of pine boards, and the fourth side will be made of galvanized steel fencing. If the pine board fencing costs $7/running foot and the steel fencing costs $3/running foot, determine the dimensions of the enclosure that can be erected at a minimum cost. 6. It costs the American Automobile Company $12,000 to produce each automobile, and fixed costs (rent and other expenses that do not depend on the amount of production) are $20,000 per week. The company's price function is p(x) = 24,000 - 80x, where p is the price at which exactly x cars will be sold. a) How many cars should be produced each week to maximize profit? b) For what price should they be sold? c) What is the company's maximum profit? MacBook Air