$P$, $Q$, $R$ 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. $21:20$