the circle C with eqn (x-2)^2+(y-1)^2=100 has centre A (2,1) and passes through the point B (10,7). THE GRADIENT OF THE RADIUS = 10 and its tangent has an eqn y=-4/3x+61/3. line l1 9parallel to the tangent passes through the midpoint of AB at (6,4) ; y=-4/3x+12 and intersects C at P and Q. Find the length of line PQ