What is the velocity of a radio wave? I know the velocity of a microwave is 3×10^8 but does that go for all electromagnetic waves? Also, what type of a wave does a sodium vapor lamp giving off yellow light emit and a helium laser emit?

The man of mass m1 and the woman of mass m2 are standing on opposite ends of the platform of mass m0 which moves with negligible friction and is initially at rest with s = 0. the man and woman begin to approach each other. derive an expression for the displacement s of the platform when the two meet in terms of the displacement x1 of the man relative to the platform.