Kepler's Laws of Planetary Motion

A planet revolves about the sun in elliptical orbit. The areal velocity $\left(\frac{\mathrm{d}A}{\mathrm{d}t}\right)$ of the planet is $4.0\times {10}^{16} {\mathrm{m}}^2 {\mathrm{s}}^{-1}$. The least distance between planet and the sun is $2\times 10^{12} \mathrm{m}$. Then the maximum speed of the planet in $\mathrm{km} {\mathrm{s}}^{-1}$ is-

Two identical planets are orbiting around a star in elliptical paths having their semi-major axes in the ratio of $1: 9.$ If life of man on $1^{st}$ planet is $80$ years then what will be his life on $2^{nd}$ planet in terms of that planet's year? (Approximate the answer to the nearest integer)

A comet (assumed to be in an elliptical orbit around the sun) is at a distance of $0.4 \mathrm{AU}$ from the sun at the perihelion. If the time period of the comet is $125$ years, what is the aphelion distance? $\mathrm{AU}$: astronomical unit.

Supposing Newton's law of gravitation for gravitation forces $F_1$and $F_2$between two masses $m_1$and $m_2$at positions $r_1$and $r_2$read

$F_1=-F_2=\frac{r_{12}}{r_{12}^3}G{M}_0^2{\left(\frac{m_1{m}_2}{M_0^2}\right)}^n$

where $M_0$is a constant of the dimension of mass, $r_{12}=r_1-r_2$and $n$is a number? In such a case 

A planet moves around the sun (mass = $M_{\mathrm{s}}$) in an elliptical orbit such that its minimum and maximum distance from the sun are $r$ and $R$ respectively. The period of revolution of this planet around the sun is