Let the centre of a circle, passing through the points \( (0,0) \), \( (1,0) \) and touching the circle \( x^2 + y^2 = 9 \), be \( (h,k) \). Then for all possible values of the coordinates of the centre \( (h,k) \), \( 4(h^2 + k^2) \) is equal to ________.
