Machine A takes 100 hours to complete a certain job and starts that job at 7AM. After two hour of working alone, machine A is joined by machine B and together they complete the job at 12PM. How long would it have taken machine B to complete the jobif it had worked alone for the entire job?	Select the correct option:
A) 100.11
B) 10.98
C) 18.07
D) 45.01
E) 35.09

Rationale: let us assume total job = 100 units a finishes 100 units in 100 hrs ( given ) hence a ( working rate ) = 1 units / hr now given that a works for 2 hr ( so 2 units done ) then a and b finish total work in 15 hours . hence a and b finish 98 units in 15 hours . of these 1 x 15 = 15 units were done by a . hence b did 83 units in 15 hours . hence b ( working rate ) = 83 / 15 units / hr hence b takes 100 x 15 / 83 = 18.07 hours to complete the job . answer c .
Answer: C