A spring of negligible mass having a force constant k extends by an amount y when a mass m is hung from it. the mass is pulled down a little and released. the s

A spring of negligible mass having a force constant k extends by an amount y when a mass m is hung from it. The mass is pulled down a little and released. The system beings to execute simple harmonic motion of amplitude A and angular frequency o. The total energy of the mass- spring system will be (A) mA o (B) mAfo+ky 2 (C) ky (D) mAPoky 2