Provide your best answer for the following math problem. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The problem is: if 12 men or 20 women can do a piece of work in 54 days , then in how many days can 9 men and 39 women together do the work ?
20 days
24.38 days (rounded to two decimal places)