Using the method of virtual work, determine the deflection at point $D$ for the cantilever beam shown below. The support at $A$ is a pin and the support at $C$ is a roller. Note the beam depth varies such that the moment of inertia for the deep section $($length $A$ to $C)$ is $I=200$ in ${?}^4$ and for the shallow section $($length $C$ to D $)I=100i{n}^4.$ Use modulus of elasticity $E=30,000$ksi.