Consider a function f : R%? = R, (z,y) f(z,y), given by 3y YY) = . 3 Describe the level curves of this function, i.e., if we set f(z,y) = k for k R, what kind of curves do we get in the (z,y) plane depending on the value of k7 Take the same function as in part a), i.e., equation (3). Describe the cross-sectional curves at y = d for d R, i.e., if we set f(z,d) = 2, what do the curves look like in the (z, z) plane depending on the value of d