For each of the following vector fields F , decide whether it is conservative or not by computing curl F . Type in a potential function f (that is, gradient f=F ). If it is not conservative, type N.a. F(x,y) = (4x+3y)i+(3x+6y)jf(x,y) = ?b. F(x,y) = 2yi+3xjf(x,y) = ?c. F(x,y) = 2xi+3yj+kf(x,y) = ?d. F(x,y) = (2siny)i+(6y+2xcos(y))jf(x,y) = ?e. F(x,y) = 2x^2i+3y^2j+3z^2kf(x,y) = ?