Please answer 5, 6 a and b with shown work. Thank you

5. Determine the intervals of increase and decrease for the function f(x) = -x - 2 sin x on the domain O sxs 2n Express intervals in interval notation. [4] 6. A scout is selling cookies throughout the summer. Suppose the number of cookies sold is given by the function n(x) = x3"* + 3 where the price, x, in dollars determines the number of cookies sold per day, n, in hundreds. a) What is the price that maximizes the number of cookies sold? [3] b) How many cookies are sold at this price? [1]