Im getting stuck on this physics problemA small rocket to

I’m getting stuck on this physics problem:A small rocket to gather weather data is launched straight up. Several seconds into the flight, its velocity is 120 m/s and it is accelerating at 18 m/s^2. At this instant, the rocket’s mass is 48 kg and it is losing mass at the rate of 0.5 kg/s as it burns fuel. What is the net force on the rocket? HINT: Newton’s second law was presented  in a new form in this chapter.The new form of Newton’s second law present is F = dP/dt, or the change in momentum over the change in time. I’m treating the gas and the rocket as a closed system, so momentum is conserved. The mass of the gas is equal to 0.5t, and the mass of the rocket is equal to the initial mass minus the mass of the gas. But, I have too many unknown variables. The initial mass, the change in time, and the velocity of the gas at the instant presented here.