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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?

- $10:11$
- $11:10$
- $20:21$
- $21:20$