physics: static friction

An air-track glider of mass 0.092 kg is attached to the end of a horizontal air track by a spring with force constant 22.5 N/m.

(a) With the air track turned off, the glider travels 8.9 cm before it stops instantaneously. How large would the coefficient of static friction μs have to be to keep the glider from springing back to the left?

(b) If the coefficient of static friction between the glider and the track is μs= 0.57, what is the maximum initial speed v1 that the glider can be given and remain at rest after it stops instantaneously? With the air track turned off, the coefficient of kinetic friction is μk= 0.50.