Problem 1: a) Find the unit normal to the surface 2x²+4yz - 5z² = -10 at the point P(3,-1,2). b) Find the equation of the tangent plane to the surface x3 + 3xy + z² = 11 at the point on the surface P(1,2,2). c) Find the equation of the tangent plane to the surface sin(xy) + 2cos(yz) + 3x = 4 at the point on the surface P(1,π/2,1).