Question 1122721
In 1 hour she does 1/9 of the whole
C does 1/x of the hole in 1 hour
completion takes 4.74 hours
4.74/9+4.74/x=1, where 1 is the entire project
multiply by 9x
4.74x+42.66=9x
4.26x=42.66
It takes Castel 10.01 hours to dig it alone.
in 1 hour approximately 0.11+0.1 or 0.21 of the hole.  In 4.74 hours, 100%.