Patrick is constructing the circumscribed circle for △rst. which construction could be his first step?

Steps in constructing a circumscribed circle on a triangle using a just a compass and a straight edge.
1) construct a perpendicular bisector of one side of ΔRST.
2) construct another perpendicular bisector of another side of ΔRST
3) the point where the two bisectors intersect will be the center of the circle.
4) place the compass on the center point, adjust its length to ensure that any corner of the triangle will be reached and draw the circumscribed circle.