In an exciting game, a baseball player manages to safely slide into second base. The mass of the baseball player is $82\mathrm{.}5$ kg and the coefficient of kinetic friction between the ground and the player is $0\mathrm{.}45.$

$($a$)$

Find the magnitude of the frictional force in newtons.

$($b$)$

It takes the player $1\mathrm{.}8$ s to come to rest. What was his initial velocity $($in m$/$s$)?$