Discussion

Explanation:

6 technicians → 10 hours to 1 job

∴ 1 technician → 60 hours to 1 job

∴ In 6 hrs (11 a.m. - 5 p.m.)6 technicians → ${\frac{3}{5}}^{th}$ of the work.

In the hour after 5p.m.,

7 technicians → ${\frac{7}{60}}^{th}$ of the job.

In the nect hour, 9 technicians will complete ${\frac{9}{60}}^{th}$ of the job.

∴ In 3 hours after 5:00 p.m. → $\frac{24}{60}={\frac{2}{5}}^{th}$ of the job is complete.

∴ At the end of 9^th hour i.e. 8:00 p.m. the work is complete.

Hence, option (d).

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