A recent storm has filled the crawlspace beneath a house with a mud that needs to be removed. A worker gets down in the crawl space with a bucket (negligible weight) that has holes in it, and fills it with mud weighing 4 lbs. He lifts the bucket, but the mud pours out the holes in the bucket at a constant rate. If the worker lifts the mud to a height of 3 feet, but only 2 pounds of the stuff remains in the bucket, find the work done in lifting the mud.