An object is released from rest when it is at an altitude of $4\mathrm{.}0\backslash$times $106$ m above the surface of a planet of mass $4\mathrm{.}0\backslash$times $1024$ kg and radius $5\mathrm{.}0\backslash$times $106$ m$.$ What is the speed of the object just before striking the surface of the planet? Neglect air resistanceA$)6\mathrm{.}9$ km$/$sB$)7\mathrm{.}8$ km$/$s$-$C$)3\mathrm{.}5$ km$/$sD$)5\mathrm{.}4$ km$/$sE$)4\mathrm{.}1$ km$/$s