Find the acceleration of our galaxy due to the nearest comparably sized galaxy. The approximate mass of each galaxy is $8 \times 10^{11}$ solar masses,and they are separated by $2 \times 10^6$ light-years. Each galaxy has a diameter of $10^5$ light-years. (Assume $1 \text{ light-year} \approx 10^{16} \text{ m}$,gravitational constant $G \approx 10^{-10} \text{ Nm}^2/\text{kg}^2$,and mass of the Sun $= 2.0 \times 10^{30} \text{ kg}$)

• A
  $4 \times 10^{-13} \text{ m/s}^2$
• B
  $2 \times 10^{-13} \text{ m/s}^2$
• C
  $5 \times 10^{-15} \text{ m/s}^2$
• D
  $5 \times 10^{-13} \text{ m/s}^2$