The maximum and minimum distances of a comet from the sun are $1.4 \times {10^{12}}m\,and\,6 \times {10^{10}}m$ respectively. If its velocity nearest to the sun is $7 \times {10^4}{\rm{m}}{{\rm{s}}^{ - 1}}$, what is the velocity in the farthest position? Assume the paths of comet in both instantaneous positions are circular