4. A spline curve p(u), O S u S 1, with two parametric cubic curve segments pa(t), pb(t), 0 S t S 1, are to be constructed through the points p0 = [0 0 0 1], p1 = [1 O 0 1], and p2 = [2 0 0 1] such that pa(t) passes through p0 and p1, whereas pb(t) passes through p1 and p2. The curve tangents at p0 and p2 are po' = [O 1 0 0], and p2' = [0 1 0 0], and pa(t) and pb(t) are C2 continuous at p1. A ruled surface s(u, v), 0 S u, v S 1, is constructed between p(u) and a straight line q(u) dened between qo = [0 0 5 1] and q1=[0 5 51]. (a) Determine the curve tangent of the curve p(u) at pl. (6 marks) (b) State a function relating t and u for the curve pa(t). (2 marks) (c) Determine the surface point s(0.25, 0.5). (12 marks)