This problem will give you a taste of how we model gravitational lens systems to measure galaxy masses. Imagine you observe a galaxy lens system with distances Dl = 940Mpc and Ds = 1745Mpc. One image appears at an angular position of θ = 1.05" from the lens galaxy, while the other appears at an angular position θ = -0.35" on the opposite side of the galaxy. You may assume the lens is circularly symmetric.

a. Assume the galaxy can be modeled as a point mass. Find the Einstein radius and mass of the lens galaxy.