1. The problem statement, all variables and given/known data 3. The attempt at a solution The first part is fairly simple I think. It's just rate of accumulation = rate of generation - rate of output(losses) I'm not too sure how to solve this differential equation. I divide the whole equation through by mc and rearrange but I keep getting an extra constant and I have no idea what to do with it. I get someone in the form dtheta/dt + P(t)theta = Q(t) + constant and I have no idea how to solve that. Any help will be appreciated, thank you.