Problem 4. The table of values below shows the weekly sales 8 (in dollars) of a company that spends $9: per week on online advertising and $y per week on tv advertising. x 500 1000 1500 2000 500 3980 5250 6180 6930 y 1000 6930 9150 10800 12100 1500 9590 12700 14900 16700 2000 12100 15900 18700 21000 83 (a) Estimate . What does this tell you about the company's sales? In 35\" (m,y)=(1000,1500) particular, would it make sense for the company to increase the amount it spends on online advertising? 88 (b) Estimate . What does this tell you about the company's sales? In 6y (m,y)=(1000,1500) particular, would it make sense for the company to increase the amount it spends on tv advertising? (c) Estimate the company's sales when :1: = 900 and y = 1700. Problem 5. Shown below is a contour graph of a function 2 = f (a), y). (a) Estimate the value of f$(1,2). (b) Estimate the value of fy(1, 2). (c) Use your answers to estimate the value of f (1.5, 3). Problem 6. Consider the surface 2 = f (:3, y) shown below. Find the signs of each of the following. (Note: the mam's is pointing into the paper to the right and the yaxz's is pointing into the paper to the left.) (a) ft(3,3) (b) fix3,3) (C) fr$(_333) (d) fyy(_3:3)