Solve the linear representation problem

My idea is:

1)b can be represented by A 1, A2, ..., am, but it cannot be represented linearly by vector group (I), which means that am has nothing to do with vector group (I) linearly, so am cannot be represented linearly by (I).

2)b is A 1, A2, ..., am and am must be used, so am can be expressed linearly by (II).