Question 1030165
Use the arc length formula:  {{{s = r*theta}}}

==>   {{{s = 20*theta}}} ==>   {{{ds/dt = 20*(d(theta)/dt)}}}

==>  {{{ds/dt = 20*400 = 8000}}} m/min

This is equal to 4.8 x {{{10^5}}} mph.