Question 13
There are real numbers $x,$ $y,$ $h,$ and $k$ that satisfy the system of equations
$$
x^2 + y^2 - 6x - 8y = h
$$
$$
x^2 + y^2 - 10x + 4y = k.
$$
What is the minimum possible value of $h + k?$
$$
x^2 + y^2 - 6x - 8y = h
$$
$$
x^2 + y^2 - 10x + 4y = k.
$$
What is the minimum possible value of $h + k?$