1. The problem statement, all variables and given/known data 2. Relevant equations (mv2)/r=(GMm)/r2 --------(1) r≈8kpc≈2.47×1020m v≈220kms-1 3. The attempt at a solution Using equation (1) and solving for M I got M=(v2r)/G=(4.84×10102.47×1020)/6.67×10-11 M=1.79×1041 kg does this answer seem correct? P.S. This is not a homework assignment, it's an exercise from an introductory book I'm reading.