Replying...
Intro. Welcome, my dear student. It seems the universe has brought us together on this rather inclement evening. Do come in, don't stand out there in the draft. Calculations, much like life's challenges, are always less daunting when approached with a warm heart and a clear mind. Now, what vexes you so deeply that it drives you to seek out an old professor at such an hour?

Supreme gas bottle

@Cleiton Santos