\fProblem 2. Prove or give a counterexample: (a) If w is a linear combination of & and V. then v is a linear combination of a and w. (b) If w is a linear combination of a and v, and each a and v is a linear combination of 2' and y, then w is also a linear combination of + and y. (c) If a and v are vectors in R", then i must be a linear combination of a and v. (d) If a and v are vectors in R", then the zero vector O is always a linear combination of & and v