The system shown starts from rest, and each component moves with a constant acceleration. If the relative acceleration of block $C$ with respect to collar $B$ is $60 \mathrm{mm} / \mathrm{s}^{2}$ upward and the relative acceleration of block $D$ with respect to block $A$ is $110 \mathrm{mm} / \mathrm{s}^{2}$ downward, determine $(a)$ the velocity of block $C$ after $3 \mathrm{s},(b)$ the change in position of block $D$ after $5 \mathrm{s}$.