The value of W that results in the collapse of the beam

The value of W that results in the collapse of the beam shown in the following figure and having a plastic moment capacity of M_p is

Indeterminacy = 1
∴ no. of plastic hinge for mechanism = 2 (at A & C)

In ∆ABD & CBE

	AD	=	AB
	CE		CB

∴ CE =	M_P.3	=	3M_P
	10		10

∴ M_P +	3M_P	=	ω × 7 × 3
	10		10

⇒ ω =	13M_P
	21