Impulses and average forces, roundabout question?

Large limestone caverns have been formed by dripping water. (a) IF water droplets of 0.030 mL fall from a height of 5.0m at a rate of 10 droplets per minute, what is the average force exerted on the limestone floor by the droplets of water during a 1.0 minute period. (b) Compare this force to the weight of one... show more Large limestone caverns have been formed by dripping water.
(a) IF water droplets of 0.030 mL fall from a height of 5.0m at a rate of 10 droplets per minute, what is the average force exerted on the limestone floor by the droplets of water during a 1.0 minute period.
(b) Compare this force to the weight of one water droplet.

My professor listed the answer as:
(0, 3b/5)
And I'm thinking... huh? Does he mean there is no force being exerted? Does that mean that the water droplets are hitting the floor and not going back up?

Not sure how to begin doing this problem. Should I convert the mL to a form of mass first? (density of the water isn't given, thouhg...)
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