Two scuba diving instructors charge money for each hour of work, plus a one-time fee for private lessons. Instructor Tommy charges according to this graph:

Instructor Bobby charges according to this table:
a) How much does Tommy cost for each hour of work, and what is his one-time fee? Show or explain your reasoning.

b) How much does Bobby cost for each hour of work, and what is his one-time fee? Show or explain your reasoning.

c) Can Tommy and Bobby every charge the same total for the same amount of time? Explain and show your reasoning.