The accompanying figure shows the velocity versus time curve for a rocket in outer space where the only significant force on the rocket is from its engines. It can be shown that the mass (in slugs) of the rocket at time seconds satisfies the equation where is the thrust (in lb) of the rocket’s engines and is the velocity (in ) of the rocket. The thrust of the first stage of a Saturn V rocket is lb. Use this value of and the line segment in the figure to estimate the mass of the rocket at time .

(click to enlarge)