An $3\mathrm{.}0$kg$$object is dropped from a height of $4000$km above a planet with mass $4\mathrm{.}0$x $1024$kg and radius of $5\mathrm{.}0$x $106$m$.$

a$)$What is the acceleration due to gravity on this planet?

b$)$ What will be its kinetic energy just as it strikes the surface?$$