Camille and Laurence can each mop the floor and vacuum the carpets at their house in 2 hours. Gaston needs 3 hours to do this same job by himself. If Camille, Laurence, and Gaston work together, how long will it take them to clean the house?

a) 1.2 hours
b) 1.5 hours
c) 1.8 hours
d) 2 hours