Two drones are flying in circular orbits around a tall structure at a constant altitude. Drone A has a circular orbit with radius (2r) and takes time (4T) to complete one full revolution around the structure. Drone B has a circular orbit with radius (2r + Δr) and takes time [4T + ΔT] to complete one full revolution, where Δr is much smaller than r and ΔT is much smaller than T. Determine the relationship between the changes in their revolution times and path radii.

A planet named Zeta orbits a distant star, called Omicron, in the Andromeda Galaxy. Zeta follows an elliptical path with a period of 8.4 years and an eccentricity of 0.76. At its closest approach during 2015, Zeta was merely 90 AU from Omicron ($1AU=1.50\times {10}^{11}$ m). Calculate the mass m of the star Omicron, assumed to be a typical massive star. Express m in kilograms and in terms of solar masses $m_{solar}$. Use: Mass of the Sun = $1.989\times {10}^{30}kg$.