Susan and Jim both babysit. Susan earns $15 for 2 hours of babysitting and $30 for 4 hours of babysitting. Jim charges a set fee of $10 plus an amount per hour. His fee in dollars, f, for h hours of babysitting is given by the equation f = 7h + 10. Which statement is true?

A) Jim charges $10.00/hour, which is higher than Susan's hourly rate.
B) Susan charges $7.50/hour, which is higher than Jim's hourly rate.
C) Jim charges $7.00/hour, which is higher than Susan's hourly rate.
D) Susan charges $7.00/hour, which is equal to Jim's hourly rate.