Use the table to solve.
 
Kevin's Supply List for
a Saltwater Aquarium 40-gal tank $170 Aquarium light $30 Filtration system $65 Thermometer $2 10-lb bag of gravel $13 Large rocks $3 per lb Clown fish $20 each Damselfish $7 eachKevin bought 6 bags of gravel to cover the bottom of his fish tank. He has 7 pounds of gravel left over. How much gravel did Kevin use to cover the bottom of the tank?