Suppose that you want to know how much gasoline is in an underground tank. You pour in 1 gallon of gasoline that contains some radioactive material with a long half-life that gives off 5000 counts per minute. After waiting until the next day for this gallon to be thoroughly mixed, you remove 1 gallon from the tank and measure its radioactivity to be 10 counts per minute. How much gasoline is in the tank?