Answer with Explanation:

(P + Q + R)'s 1 hour's work = ( 1/8 + 1/10 + 1/12 ) = 37/120 .

Work done by P, Q and R in 2 hours =(37/120 x 2 ) = 37/60 .

Remaining work = (1 -37/60) = 23/60 .

(Q + R)'s 1 hour's work = (1/10 + 1/12) = 11/60 .

Now,11/60 work is done by Q and R in 1 hour.

So,23/60 work will be done by Q and R in (60/11 x 23/60 ) = 23/11 hours = 2 hours.

So, the work will be finished approximately 2 hours after 11 A.M., i.e., around 1 P.M.

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