Paint spills onto a floor in a circular pattern. the radius of the spill increases at a constant rate of 2.5 inches per minute. how fast is the area of the spill increasing when the radius of the spill is 18 inches?
a) 5pi in^2/min
b) 36pi in^2/min
c) 45pi in^2/min
d) 90pi in ^2/min