QUESTION $2$: Plastic analysis & design of a continuous beam

The continuous beam shown in the Figure below must support the loads shown with a collapse load factor of

$=1\mathrm{.}4.$ Consider the governing work equation for collapse of each span to determine the corresponding plastic

moment capacity $M_p.$ Determine the critical span and the required plastic moment capacity $M_p$ to prevent

collapse by any one of the possible collapse mechanisms. Bending moment diagram at collapse in not required.

Figure $2$