Bezier and B-Spline surfaces

Consider the control mesh mesh.
a) Plot a Bezier surface (Subscript[f, 1])(t,s) given by the control mesh. What is the degree of the surface?
b) Plot a B-Spline surface (Subscript[f, 2])(t,s) of degree (2,3) given by the control mesh and knot vectors {0,0,0,1/2,1,1,1} and {0,0,0,0,1/2,1,1,1,1}
c) Plot a B-Spline surface (Subscript[f, 3])(t,s) of degree (2,2) given by the control mesh and knot vectors {0,0,0,1/2,1,1,1} and {0,0,0,1/4,1/2,3/4,1,1,1}
c) Find a point on (Subscript[f, 1]) using the  DeCasteljau algorithm

mesh= Transpose[{{{0,-2,1},{0,-1,1},{0,0,1},{0,1,1}},{{1,-2,1},{1,-1,1},{1,0,1},{1,1,1}},{{2,-2,1},{2,-1,1},{2,0,1},{2,1,1}},{{3,-2,1},{3,-1,1},{3,0,1},{3,1,1}},{{4,-2,1},{4,-1,1},{4,0,1},{4,1,1}}}+Table[Table[{RandomReal[{-0.2,0.2}],RandomReal[{-0.2,0.2}],RandomReal[{-1,1}]},{i,1,4}],{j,1,5}]];
MatrixForm@mesh