Painter a Can Paint a House in 12 Hours, Painter $1 \frac { 1 } { 2 }$

Essay

Painter A can paint a house in 12 hours, Painter B can paint the same house in 8 hours, and Painter C can paint the house in 10 hours. How many hours will it take to paint the house if Painter A has to leave after working $1 \frac { 1 } { 2 }$ hours and Painter C arrives 4 hours after Painter A and Painter B start the job.