The total cost of paying off any loan depends on the size of the annual interest rate applied to the loan. If we set x to denote the annual interest rate, multiplied by one hundred, so that x% = x/100 is the annual interest rate, and if we set y to denote the total cost of paying off a car loan of 30000 dollars, then the function y = f(x) represents the relationship between the total cost y of the loan and the size of the annual interest rate, y. a) Interpret the meaning of f (7 +1/8)= 50000. b) Interpret the meaning of f'(x) (the derivative function). c) Considering that the inputs x of the function are measured in percentage points (one unit equal to one percent) and the outputs y = f(x) are measured in dollars, what are the units (of measurement) of the derivative function? d) What is the sign, minus or plus, of f'(x)? Explain in carefully chosen words, all your answers to the above questions.