6. (12points) Wheat production Wfim a: given year depends on the average temperature T and the annual rainfall R Scientists estimate that the average temperature Is rising at a rate of 0.12 C/ year and rainfall\" Is decreasing at a rate of 0.20 cm / year They also estimate that, at current production levels, = 2 and 2P?- = 6. 67' BR .. . a. What is the signicance of the signs of these partial derivatives? Explain b. EstImate the current rate of wheat production, \"(It [Chain Rule]