A 4 kg roller is attached to a massless spring of spring constant k = 100 N/m. It rolls without slipping along a frictionless horizontal road. The roller is displaced from its equilibrium position by 10 cm and then released. Its maximum speed will be
(a) 0.5 m/s
(b) 0.6 m/s
(c) 0.4 m/s
(d) 0.8 m/s