How large is the Schwarzschild R adius for a 100 solar mass black hole? (in km)

1) How large is the Schwarzschild Radius for a 100 solar mass black hole? (in km)

Vesc = velocity needed to escape, in m/s

G = a constant, 6.67 x 10-11 N m2/kg2

M = mass of the object you are escaping from, in kg

R = radius of the object you are escaping from, in m

R = _____ Km

2) what formula is correct for the question above 

a) 

b)  

c) Other formula was used d)  I have my own  (if you choose d please list your formula. Also include the applycation you used to get the answer for the question above. 

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Please show your work (optional)

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