The negative partial derivative for means that increasing the temperature decreases wheat production and decreasing the temperature increases wheat production. The positive partial derivative for \frac {\delta W}{\delta R} means that as rainfall increases, wheat production will increase and that as rainfall decreases, wheat production will decrease.a) what is the significance of the signs of the partials?

I think they just want you to apply the chain rule for part b: you have , , and . You will also need to add the impact of each of the factors on wheat production.