Let b = (3,1, 2, l)7. Find the closest point and the distance from b to the

Question:

Let b = (3,1, 2, l)7. Find the closest point and the distance from b to the following subspaces:
(a) The line in the direction (1. 1. 1. I)T,
(b) The plane spanned by (1,1,0,0)T and (0.0, 1, l)T,
(c) The hyperplane spanned by (1,0,0,0)T, (0. 1.0. 0)T, (0, 0, l,0)T,
(d) The hyperplane defined by the equation
x + y + z + w = 0.