[问答题]
Derive a formula for the mass of a :4 9ht-kfgd * w6 uz)wngiqhm2p fz je/brnak ,o-3w*p, 8 k1/2vdyfhlglanet in terms of its radius r, the acceleration due to gravity at its surface and the gravitational constant G./v,, g3ybe fr-wzkno* f2/kd8jph al1
