In 1905 a Bohemian farmer accidentally allowed several muskrats to escape an enclosure Their population grew and spread occupying increasingly larger areas throughout Europe In a classical paper in ecology it was shown by the scientist Skellam 1951 that the square root of the occupied area increased at a constant rate k Determine the rate of change of the distance from the site of release that the muskrats had spread For simplicity you may assume that the expanding area of occupation is circular with radius r t Simplify your answer so that it only depends on k r t