Working together, A and B can do a job in 6 days. B and C can do the same job in 10 days, while C and A can do it in 7.5 days. How long will it take if all A, B and C work together to complete the job?  Options:
A) 4 days
B) 5 days
C) 8 days
D) 9 days
E) 10 days
A and 5 days 1day work = 1/6   5 days and C 1day work = 1/10   c and A 1day work =1/7.5   A,5 days,C 1day work =(1/6 + 1/10 + 1/7.5)*1/2=1/5   so A.5 days.C completes work in 5 days   ANSWER:5 days
<result>B</result>
Working together, A and B can do a job in 6 days. B and C can do the same job in 10 days, while C and A can do it in 7.5 days. How long will it take if all A, B and C work together to complete the job?