Elena (60. 0 kg) and madison (65. 0 kg) are ice-skating at the rockefeller ice rink in new yok city. Their friend tanner sees elena move to the right with a speed of 1. 20 m/s towards madison. Madison is moving to the left at a speed of 2. 50 m/s towards elena. What is elena's momentum? (assume the positive direction is to the right and the negative direction is to the left. ).