The correct answer is (a) 0.1625.
To calculate the average number of units of work completed per worker per minute, we first need to calculate the total number of units of work completed by each worker. Worker A completes 1 unit of work in 4 minutes, so in 1 minute, he completes 1/4 unit of work. Worker B completes 1 unit of work in 5 minutes, so in 1 minute, he completes 1/5 unit of work. Worker C completes 1 unit of work in 6 minutes, so in 1 minute, he completes 1/6 unit of work. Worker D completes 1 unit of work in 10 minutes, so in 1 minute, he completes 1/10 unit of work. Worker E completes 1 unit of work in 12 minutes, so in 1 minute, he completes 1/12 unit of work.
The total number of units of work completed by all five workers is 1 + 1/5 + 1/6 + 1/10 + 1/12 = 11/12. The average number of units of work completed per worker per minute is therefore 11/12 / 5 = 0.1625.
Option (b) is incorrect because it is the average number of units of work completed per worker per hour, not per minute. Option (c) is incorrect because it is the average number of units of work completed per worker per day, not per minute. Option (d) is incorrect because it is the average number of units of work completed per worker per week, not per minute.