$5$ A $3\mathrm{.}0$ kg block sliding on a horizontal surface is accelerated by a compressed spring. At first, the block slides without friction. But after leaving the spring, the block travels over a new portion of

the surfice, with a coefficient of kinetic friction ${}_1=0\mathrm{.}20,$ for a distance of $80$ m before coming to rest $($ Fig $-3).$ The force constant of the spring is $120\frac{N}{m}.$

$($a$)$ What was the maximum kinetic energy of the block?

$($b$)$ How far was the spring compressed before being released?