Could you show me the steps to solve this please?

For architectural reasons, a certain rectangular simply supported c$/$c beam B$2$ is limited in cross section to a width of $250$ mm and a total depth of $450$ mm$.$ It must carry a total service

live load of $20$ KN$/$m and total dead load $($including its own weight$)$ of $15$ KN$/$m$.$ If fc$\text{'}=35$ MPa and fy $=420$ MPa.

Design Using Ultimate Strength Design Method for Flexural reinforcement and Shear reinforcement?