4. Consider the surface S parameterized by the vector r(u, v)= ui + vj+uk for {0 u2,0 v2). (a) Calculate the surface normal vector N(u,v) using r(u, v) (b) Calculate the unit surface normal vector n(u, v) = N(u, v)/|N(u, v)| (c) Evaluate the unit surface normal vector n at the point (x,y,z) = (3/2,3/2,9/4). Hint: What (u, v) pair is associated with this (x,y,z) point?