Answer:
60 man-days
Explanation:
Lets find a rate that will be in units of (man-days/job).
"5 men can complete half of work within 6 days" can be written mathematically as:
(5 men)*(6 days)/(0.5 job)
which reduces to: 30 man-days/0.5 job, or 60 man-days/job
The work in man days for a complete job would therefor be 60 man-days.
(1 job)*(60 man-days/job) = 60 man-days