Which factor is primarily responsible for Earth's seasons according to Newton's Law of Gravity?

Three meteorites in outer space lie along a straight line. At a certain instant in time, the meteorite on the right is 53 m from the center meteorite and the lefthand meteorite is 21 m from the center meteorite. If the mass of the righthand meteorite is 1300 kg and the net gravitational force on the center meteorite is zero, what is the mass of the lefthand meteorite?

(II) Two objects attract each other gravitationally with a force of 6.5 x 10^-9 N when they are 0.25 m apart. Their total mass is 6.50 kg. Find their individual masses.