Plz answer ASAP will $100\%$ upvote The gravitational potential energy, in Joules, of a rocket above earth's surface can be calculated by $E_G=-\frac{GMm}{r}$

where $G$ is the universal gravitational constant $(6\mathrm{.}67{10}^{-11}N\frac{m^2}{k}{g}^2),M$ is the mass of the earth $(5\mathrm{.}98{10}^{24}(kg)),m$ is

the mass of the rocket in $kg,$ and $r$ is the distance from the earth's centre. The radius of the earth is $6\mathrm{.}38{10}^{6}m.$

The mass of the rocket decreases while it is ascending as it is burning fuel. Consider a rocket for which the mass

changes linearly $($in real rockets it doesn't!$)$ and the total mass of the rocket can be obtained by the equation $m=$

$15000-60(t)$ where $t$ is the time since take$-$off, in seconds.

a$.$ Determine the gravitational energy of this rocket if it reached height of $200km$ above the earth's surface in $120s.$

b$.$ Determine the average rate of change of gravitational energy of the rocket from $120$ to $125$ seconds, assuming it

ascends another $10km$ during that time. PPPPppp