Design a Roof Beam $($using a UK UB section in S$275$ steel$)$ that has sufficient capacity, and meets the totaldeflection limit specified by the client $($span$/250).$ Use Plastic design where possible, and ensure thatyour design calculations consider all appropriate modes of failure. The client wishes to minimise theenvironmental impact of the Assembly Hall, and requires the Roof Beam chosen to be the Beam $($UB$)$which uses the lowest amount of steel $($hence the lightest possible beam$)$ whilst meeting the capacitychecks and deflection limit$.$ a $=7$m$,$ b $=2$m$,$ c $=3$m$,$ P$($Crane Load$)=20$KN