Hi I just got stuck on this question, would appreciate if I can get some guidance

Suppose social well-being is determined by the functionu(x₁,x₂, . . . ,x_N) wherex_iis the quantity of public serviceiprovided by the government.

How many first-order partial derivatives does U have? pick one of these and explain in words what it represents in the context of social well-being and public service provision.

Thanks