For any triangle T in the xy–coordinate plan, the center of T is defined to be the point whose x–coordinate is the average (arithmetic mean) of the x–coordinates of the vertices of T and whose y–coordinate is the average of the y–coordinates of the vertices of T. If a certain triangle has vertices at the points (0,0) and (6,0) and center at the point (3,1), what are the coordinates of the remaining vertex?
Options
A) (3,3)	B) (3,6)	C) (4,9)	D) (6,4)	E) (9,6)
Let (a,b) be the remaining vertex.   x: 0 + 6 + a = 3*3. Then a = 3.   y: 0 + 0 + b = 3*1.= 
<gadget id="calculator">3*1.</gadget>
<output>3</output>
3.   The answer is (3,3).
<result>A</result>
For any triangle T in the xy–coordinate plan, the center of T is defined to be the point whose x–coordinate is the average (arithmetic mean) of the x–coordinates of the vertices of T and whose y–coordinate is the average of the y–coordinates of the vertices of T. If a certain triangle has vertices at the points (0,0) and (6,0) and center at the point (3,1), what are the coordinates of the remaining vertex?