A circle with a circumference of $42 \mathrm{~cm}$. Consider the circle below.

What is the diameter $D$ of the circle?

Round your answer to two decimal places.
Please directly answer the question and provide the final value, e.g., 1, 2.5, 300.
Question: A circle with a circumference of $42 \mathrm{~cm}$. Consider the circle below.

What is the diameter $D$ of the circle?

Round your answer to two decimal places.
Please first conduct reasoning, and then answer the question and provide the final value, e.g., 1, 2.5, 300, at the end.
Question: A circle with a circumference of $42 \mathrm{~cm}$. Consider the circle below.

What is the diameter $D$ of the circle?

Round your answer to two decimal places.