Stars: If a Spherical Galaxy of Diameter 100,000 Ly Contained

Stars: If a spherical galaxy of diameter 100,000 ly contained enough mass to be a black hole having a Schwarzschild radius equal to that of the galaxy, what would be its mass? (G = 6.67 × 10^-11 N ∙ m²/kg², 1 ly = 9.461 × 10¹⁵ m, c = 3.00 × 10⁸ m/s)

A) 200 × 10⁹ kg
B) 400 × 10⁹ kg
C) 6.9 × 10²³ kg
D) 3.2 × 10⁴⁷ kg
E) 6.4 × 10⁴⁷ kg