Given the task definition and input, reply with output. In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: working alone , tom finishes cleaning half the house in a third of the time it takes nick to clean the entire house alone . tom alone cleans the entire house in 6 hours . how many hours will it take nick and tom to clean the entire house if they work together ?
Options: a ) 1.5 , b ) 2 , c ) 2.4 , d ) 3 , e ) 3.6
e