Please compute the answer of the given Problem

Problem-A piston-cylinder contains oxygen gas that is initially at 77°C. The gas expands, resulting in a final temperature and pressure of 40°C

and 5 bars. The gas is modeled as ideal with PVn =constant and n=1.3.

Part 1- Determine the initial pressure [bar] as well as the work and heat transfer [kJ/kg].

I want experts help to find the initial pressure at bar.