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$A$ and $B$ can complete a task in $30$ days when working together. After $A$ and $B$ have been working together for $11$ days, $B$ is called away and $A$, himself completes the task in the next $28$ days. Had $A$ been working alone, the number of days taken by him to complete the task would have been:

- $\dfrac{379}{9} \\$
- $\dfrac{840}{19} \\$
- $\dfrac{520}{11} \\$
- $\dfrac{590}{11}$