Question 15. The price of a volleyball is given by p(v) = 50 - 1.25v and the cost is C(v) = 160 + 10, where u is the number of vollyballs in thousand and cost is in dollars. (a) Find the rate of change of the profit P(v). (b) Find and interpret P'(5). (c) Find and interpret P'(20). (d) Notice that the answer to part (a) is positive and the answer to part (b) is negative. What does this tell you about how many volleyballs should be sold? Question 16. A company find that its total costs are related to the amount spent on training programs by T(x) = 1000 + 60x , where T(x) is costs in thousands of dollars when a hundred dollars are spent on training. 4x + 5 (a) Find T'(x) (b) Find and interpret T'(900). (c) Find and interpret T'(1900).Question 17. Since its inception in 1971, Socially Responsible Investments (SRIs) have yielded returns to investors on par with investments in general. The assets of socially responsible funds (in billions of dollars) from 1991 through 2001 is given by f (t) = 23.7(0.2t + 1)1.32, 0