Problem $1\mathrm{.}3\mathrm{.}174$

Tev cars of the same mass run head$-$on into each other at $C.$ Afler the coilision, the cars skid with their brakes locked and comic sor a sopp in the positiuns shoun it the lower part of the figue. Knowing that the spord of car A just hefore impact was $5m\frac{m}{a}nsl$ that the coefreicut of binetse friction betueen the pavemem and the lires of both can is $0\mathrm{.}30.$ deseminc $($a$)$ the spoul of tar A just helore impact, $(b)$ the effective cacificient of revitution beeween the twe cars.