A rock is thrown on earth with an initial horizontal velocity and it hits the ground at x meters away from the point where the stone is thrown. What if:

(a) The same stone is thrown with the same initial conditions but on another planet. On the new planet the thrown distance is 0.3 times the distance x on the earth. If the new planet has the same radius as earth, how much larger is the new planet's mass relative to earth? (i.e new planet mass= X earth mass. Find X.)

(b) The same stone is thrown with the same initial conditions but instead on another planet with the same mass as earth but with a radius 7 times the radius of the earth. With what factor will x change?