Two circles x2+y2−2x=0x^2 + y^2 - 2x = 0x2+y2−2x=0 and x2+y2−4y=0x^2 + y^2 - 4y = 0x2+y2−4y=0 intersect. What is the length of their common chord?
4/54/\sqrt{5}4/5
8/58/\sqrt{5}8/5
222
5/25/\sqrt{2}5/2