${?}^{\text{@}78}$ In the overhead view of Fig. $4-47,$ Jeeps $P$ and $B$ race along straight lines, across flat terrain, and past stationary border guard $A.$ Relative to the guard, $B$ travels at a constant speed of $20\mathrm{.}0\frac{m}{s},$ at the angle ${}_2=30\mathrm{.}0.$ Relative to the guard, $P$ has accelerated from rest at a constant rate of $0\mathrm{.}400\frac{m}{s^2}$ at the

Figure $4-47$ Problem $78.$ angle ${}_1=60\mathrm{.}0.$ At a certain time during the acceleration, $P$ has a speed of $40\mathrm{.}0\frac{m}{s}.$ At that time, what are the $($a$)$ magnitude and $($b$)$ direction of the velocity of $P$ relative to $B$ and the $($c$)$ magnitude and $($d$)$ direction of the acceleration of $P$ relative to $B?$