At what approximate temperature and pressure can all three phases of water exist simultaneously? 0°c, 760 mmhg 0°c, 5 mmhg 80°c, 380 mmhg 100°c, 760 mmhg

Contrast the force of gravity between these pairs of objects: 1-kg mass and a 2-kg mass that are 1 m apart; a 1-kg mass and a 2-kg mass that are 2 m apart; and two 2=kg masses that are 1 m apart. i dont understand.