Problem: pr is tangent to a circle at point p . q is another point on circle such that pq is diameter of circle and rq cuts circle at m . if radius of circle is 4 units and pr = 6 units . find ratio of triangle pmr to pqr . 
Options: ['a ) 11 / 20', 'b ) 3 / 5', 'c ) 13 / 20', 'd ) 18 / 25', 'e ) 18 / 26']
c