6. In the reference frame of observer A, the 4.60-kg mass is sliding in the positive x direction at 3.00 m/s. Observer B is moving toward observer A with a relative velocity of 7.00 m/s. (a) What kinetic energy does observer A calculate for the mass? (b) What kinetic energy does observer B calculate for the mass? (c) Which observer is correct? 3.00 7.00 m S 4.60 kg A B