co-geom

Let E be the ellipse
x^2/a^2 + y^2/b^2 =1

Pet P=(h,k)


two tangent lines are drawn from P to E
These two lines touch E at two distinct points A,B

a)
Let y=mx+c be a tangent to E passing through P
set up a relation between m,h,k,a,b
(just write down the answer)

b)
find the mid-pt of AB
please state the key steps involved
Can you give more than one method to do this?