There are four prime numbers written in ascending order of magnitude. The product of the first three is 385 and of the last three is 1001. Find the fourth number?

A. 4(2/3) days
B. 4 days
C. 5(1/3) days
D. 1(1/3) days
(1/A)+(1/B) = (1/6) (1/B)+(1/C) = (1/12) (1/A)+(1/C) = (1/8) Solving the three equations,
(1/A)+(1/B)+(1/C) = (3/16) Together they take 16/3 = 5(1/3) days to complete the task.