If the centroid of an equilateral triangle is (1,1) and one of its vertices is (-1,2) then, equation of its circum circle is
a. x²+y²-2x-2y-3=0
b. x²+y²+2x-2y-3=0
c. x²+y²-4x-6y-9=0
d. x²+y²+x-y-5=0