There are twenty people working in an office. The first group of five works from 8 a.m. to 2 p.m. The second group of ten works from 10 a.m. to 4 p.m. and the third group of five works from 12 noon to 6 p.m. There are three computers in the office which are frequently used by all the employees. During which of the following hours are the computers most likely to be used?

There are twenty people working in an office.

The first group of five works from 8 a.m. to 2 p.m.

The second group of ten works from 10 a.m. to 4 p.m. and the third group of five works from 12 noon to 6 p.m.

There are three computers in the office which are frequently used by all the employees.

During which of the following hours are the computers most likely to be used?

The work hours of each group:
The first group of 5 works from 8 a.m. to 2 p.m.
The second group of 10 works from 10 a.m. to 4 p.m.
The third group of 5 works from 12 noon to 6 p.m.

Here is the breakdown of overlapping periods:

8 a.m. to 10 a.m.: 5 people (first group)
10 a.m. to 12 noon: 15 people (first group + second group)
12 noon to 2 p.m.: 20 people (first group + second group + third group)
2 p.m. to 4 p.m.: 15 people (second group + third group)
4 p.m. to 6 p.m.: 5 people (third group)

So, the highest number of people is from 12 noon to 2 p.m., with all 20 employees present.

Thus, the correct answer is (a).