Given a closed convex curve, let a central convex curve circumscribe it, then what is the minimum of B/A?(A and B are their corresponding areas)

Question

I guess the answer is 2, but I cannot prove it.

I mean supermum of the minimum B/A among all A.

Notice:

Central convex curve means the convex curve is symmetric about a point in it, that is, when you rotate the curve 180 degrees about the point, it comes back to the original curve.

For triangle, which is considered the most asymmetric, 2 is a lower bound. That is why I think 2 is a lower bound for all other convex curves

I need to calculate a minimum r=B/A such that for all of the colsed convex curves，their always exists a central convex curve (with area A*r) circumscribe it. Please help me, a lot of thanks.