Four persons A, B, C and D are used to clean a building. A is twice as fast as B while C is twice as fast as D and B is thrice as fast as D. A cleans (1/8)th of the building, B cleans (1/4)th, C cleans (3/8)th and D cleans the rest. The people work one after the other and in all it takes 156 hours for them to clean the whole building. The individual times taken by A, B, C and D to clean the building (in hours) are ________.