Two equal objects (of mass m) on effectively frictionless horizontal air track are held between rigid supports by three identical springs (spring constant k) in a set up of one spring attached to each of the supports and one of the masses and the third spring between the masses. A) what is the frequency of oscillation if one of the masses is clamped down? B) what are the frequencies of the two modes of vibration when both masses are allowed to vibrate freely?