A circle is inscribed in a square. The circumference of the circle is increasing at a constant rate of 6 in/sec. As the circle expands, the square expands to keep the
circle inscribed. At what rate is the perimeter of the square increasing?

A. 12/pi in/sec
B. 18/pi in/sec
C. 24 in/sec
D. 24/pi in/sec
E. 36 in/sec