The center is (2,1,3)
the plane contains the vector (0,0,1) (because it contains the northpole) and the vector (5 , -54, 54) (because it is parallel to the line)
The normal vector (a,b,c) is orthogonal to the others vectors, then :
c = 0
and 5a - 54b = 0
then if a = 54, b = 5 and the equation is
54x + 5y = d
the center is into the plane so :
54*2 + 5*1 = d
d = 113
the equation is 54x + 5y = 113