A $0\mathrm{.}650$ kg mass is held at rest against a linear spring that is compressed by $0\mathrm{.}070$ m$.$ The spring force pushes on the mass in the $+$x direction and the mass is on a horizontal surface.

a$)$ If the mass leaves the spring with a speed of $10\mathrm{.}0$ m$/$s and the surface is frictionless, what is the spring constant of the spring?

b$)$ If the mass leaves the spring with a speed of $10\mathrm{.}0$ m$/$s and the coefficient of kinetic friction is $0\mathrm{.}750,$ what is the spring constant of the spring?