$4\mathrm{.}53$ A tension $Q$ is maintained in the cord shown as it passes over

pulleys of diameter $d.($a$)$ Neglecting the weight of the rod and pulleys,

express the magnitude of the force $P$ corresponding to equilibrium in terms

of $Q,a,d,$ and $.($b$)$ Knowing that $Q=10lb,a=5in.,d=0\mathrm{.}8in.,$ and

$=30,$ determine the magnitude $P.$