Find the centre of circle opposite to A

Find the coordinate of the centre of the circle opposite to vertex A which touch the sides of the triangle the co-ordinates of whose angular points are the points $A =( 6 , 0 ) , B =( 0 , 6 ) ,C =( 7 , 7 )$ .

The answer would be in the form of $( \frac ab , \frac cd )$ with $\text{gcd}(a,b)=\text{gcd}(c,d) = 1$ . What is the value of $a+b+c+d+1$ ?