Critical Reasoning

Helen, Jen, and Monica have offices in the same wing at work. Rick and Sam have offices in that wing as well. All of their offices are arranged in a row. There are no other offices in that wing. Monica has the first office in the wing, while Jen's office is between Helen's and Rick's.

A. Sam has the last office, and Helen's office is right next to his.
If Sam has the last office and Helen sits next to him, it follows that Jeni sits on the other side of Helen and Rick on the other side of Jen. The order of the offices would be M, R, J, H, S.
B. Rick's office is next to Monica's office.
[spoiler]If Rick sits next to Monica and Jen's office is between Helen's and Rick's, this defines all of the placements: the order is M, R, J, H, S.[/spoiler]
C. Jen has the third office.
[spoiler]This is the credited response. If Jen has the third office, we still don't know where Rick and Helen sit in relation to Jen. [/spoiler]
D. Helen has the second office.
If Helen has the second office, the order must be M, H, J, R, S.
E. Rick has the third office.
If Rick has the third office and Jen sits between Helen and Rick, then Sam must have the second office. The order goes M, S, R, J, H.

Can someone explain this further ?