A horizontal spring with force constant k = 660 Mm is attached to a wall at one end and to a block of mass m = 2.85 kg at the other end that rests on a horizontal surface. The block is released from rest from a position 4.15 cm beyond the spring's equilibrium position. (a) If the surface is frictionless, what is the speed of the block as it passes through the equilibrium position? 0.632 l y m/s (b)__I_f the surface is rough and the coefcient of kinetic friction between the box and the surface is M = 0.250, what is the speed of the block as it passes through the equilibrium position? X differs from the correct answer by more than 10%. Double check your calculations. m/s