The circle C has centre A(4,3) and passes through the point B(10, 5) .
(a) Find an equation for C.
The line L1 is the tangent to C at the point B.
(b) Find an equation for L1
The line L2 is parallel to L1 and passes through the mid-point of AB.
Given that intersects C at the points P and Q,
(c) Find the length of PQ, giving your answer in its simplest surd form.