How fast is the edge of a router bit moving?

Given a blade of diameter D inches, revolving at a rate of R rpm, a point on the perimeter of the blade will travel the length of the circumference C each revolution.

Speed = distance / time

C = pi x D

pi ~= 3.1416

Speed:

Distance/revolution x revolutions/time = C x R inches/minute

What is the speed of a 1" router blade, moving at 20,000 rpm at the perimeter. Answer must be in miles per hour.