In a trend that scientists attribute, at least in part, to global warming, a certain floating cap of sea ice has been shrinking since 1980. The ice cap always shrinks in the summer and K grows in winter. Average minimum size of the ice cap, in square miles, can be approximated by A = ar-. In 2013, the radius of the ice cap was approximately 783 mi and was shrinking at a rate of approximately 4.5 mi / yr. How fast was the area changing at that time? The area was changing at a rate of in 2013. (Round to the nearest integer as needed.)