[填空题]
Consider the Voronoi diagram below with s91cz2q jg88rtps47tu hs hof+ites A, B, C and D, anu1glv*y-3 am:dy ajz8d intersections E a3g lv-:u ydy*m18 azjand F.
1.Determine the site closest to the coordinate (9,6).
2.Determine the coordinates of the centre of the largest empty circle.
3.Calculate the area of the largest empty circle. a ≈ $units^2$