Locus

For triangle ABC, A is (0,0), B is (a, b) where b > 0 and C is (10,0). Find :
(1) The locus of the intersecting point of the angle bisector of angle ABC and the straight line x = 5 in terms of a and b.
(2) Is the y - coordinate of the intersecting point always < 0 for all values of a and b ? Please prove.