The part of the question about the size of the sponge is just there to trick you; you don't need it. All you need is the 22.5 L per day.
To find the amount of water it can pump in 1 hour, you divide the 22.5 by 24 because there are 24 hours in a day:
[tex](\frac{22.5L}{day})(\frac{day}{24hours})=0.9375\ liters\ per\ hour[/tex]
Now that we have hours, we can divide that by 60 to get the amount pumped per minute (because there are 60 minutes in an hour):
[tex](\frac{0.9375L}{hour})(\frac{hour}{60minutes})=0.015625\ liters\ per\ minute[/tex]
