Please help with full explanation.

1. Describe, with justification, the possible reduced row echelon forms of a matrix A in the following cases: (a) A is a 2 x 4 matrix whose columns span R2. (b) A is a 3 x 4 matrix whose columns span R3. (c) A is a 4 x 4 matrix whose columns span R4. 2. Let a, be R and a 0 A = b 1 a Find a spanning set for the solution set of the homogeneous system A . x = 0