Problem 3. (1 point) Your monthly car payment in dollars is P = f( Po, t, r), where $ Po is the amount you borrowed, t is the number of months it takes to pay off the loan, and r percent is the interest rate. (a) Is aP/at positive or negative? ? Suppose that your bank tells you that the magnitude of aP/at is 50. What are the units of this value? (For this problem, write our your units in full, writing dollars for $, months for months, percent for %, etc. Note that fractional units generally have a plural numerator and singular denominator.) (b) Is aP/or positive or negative? ? Suppose that your bank tells you that the magnitude of aP/Or is 5. What are the units of this value? (For this problem, write our your units in full, writing dollars for $, months for months, percent for %, etc. Note that fractional units generally have a plural numerator and singular denominator.) For both parts of this problem, be sure you can explain what the practical meanings of the partial derivatives are. Note: You can earn partial credit on this