PROBLEM $15\mathrm{.}164$

At the instant shown the length of the boom $AB$ is being decreased at the constant rate of $0\mathrm{.}2\frac{m}{s}$ and the boom is being lowered at the constant rate of $0\mathrm{.}08ra\frac{d}{s}.$ Determine $(a)$ the velocity of Point $B,(b)$ the acceleration of Point $B.$