Hi, I was just wondering if someone could tell me if I am doing the following problem correctly?

The vertices of a square are moving away from the centre at a rate of 2 cm/s. How fast is the area of the inscribed circle changing when the side of the square is 20 cm?

I let r=10 cm and plugged it into the derivative of the area of a circle... is this what I am supposed to do?

Thanks for any help