The amount of water in a barrel leaks out at a continuous rate. Initially there were 250 gallons...?

The amount of water in a barrel leaks out at a continuous rate. Initially there were 250 gallons of water in the barrel. After 4 hours there were 213 gallons in the barrel. Express the number of gallons of water in the barrel, A, as a function of the elapsed time, t, in hours. round to the nearest hundredth.