\f85. Marginal Cost If C(x) is the cost of producing x paddle- boards, explain what each of the given equations means in prac- tical terms, including units. (a) C(100) = 80,000 (b) C'(100) = 30087. Mcdonald's Revenue The revenue (in billions of dollars) generated by Mcdonald's Corp. for the years 2008 to 2015 can be approximated by R(t) = -.1+3 + 3.2512 - 3.5t + 134, where t = 8 corresponds to the year 2008. Find the rate of change of revenue with respect to time. (Data from: www.morn- ingstar.com.)