Toy GUN WIth a SPring?

A toy gun uses a spring to project a 4.5 g soft rubber sphere horizontally. The spring constant is 10.0 N/m, the barrel of the gun is 13.8 cm long, and a constant frictional force of 0.038 N exists between barrel and projectile. With what speed does the projectile leave the barrel if the spring was compressed 6.4 cm for this launch?