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P, Q, R and S are working on a project. Q can finish the task in $25$ days, working alone for $12$ hours a day. R can finish the task in $50$ days, working alone for $12$ hours per day. Q worked $12$ hours a day but took sick leave in the beginning for two days. R worked $18$ hours a day on all days. What is the ratio of work done by Q and R after $7$ days from the start of the project?

1. $10:11$
2. $11: 10$
3. $20:21$
4. $21:20$