please clear answer and state assumptions

You wish to measure the temperature and pressure of steam fl owing in a pipe. To do this task, you connect a well-insulated tank of volume 0.5m3 to this pipe through a valve (check attached image). This tank initially is at vacuum. The valve is opened, and the tank fills with steam until the pressure is 9MPa. At this point the pressure of the pipe and tank are equal, and no more steam flows through the valve. The valve is then closed. The temperature right after the valve is closed is measured to be 800C. The process takes place adiabatically. Determine the temperature (in [K] ) of the steam flowing in the pipe. When doing so, state all the assumptions you took into account and explain your choices. You may assume the steam in the pipe stays at the same temperature and pressure throughout this process