**Question** : Is the following true?

"Letting $K$ be a convex bounded closed set on a plane, then there exists a triangle $M$, which includes $K$, such that $|M|\le 2|K|$. Here, $|M|,|K|$ is the area of $M,K$ respectively."

**Motivation** : First, I've thought about the case that $K$ is a parallelogram. Then, I reached the above expectation, but I can neither prove this nor find any counterexample. Can anyone help?

**Remark** : If $K$ is a parallelogram, then $|M|\ge2|K|$ for any $M$ which includes $K$. This question has been asked previously on math.SE without receiving any answers.