What are the probabilities of planetary transits in the following systems, assuming circular orbits:
a) A 2 R(earth) planet around a sun-like star on a P=66 day orbit
b) A 1 R(earth) planet in the habitable zone (P= 1 atm, AB= 0.33) around 0.5 R(sun) star with a T(eff)= 3520 K?