Aplanet moves in an elliptical orbit around the sun. the mass of the sun is ms. the minimum and maximum distances of the planet from the sun are r1 and r2, respectively.
using kepler's 3rd law and newton's law of universal gravitation, find the period of revolution p of the planet as it moves around the sun. assume that the mass of the planet is much smaller than the mass of the sun.
use g for the gravitational constant.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."