a pebble is dropped into a calm pond, causing ripples in the form of concentric circles. The radius (in feet) of the outer is described by the...

a pebble is dropped into a calm pond, causing ripples in the form of concentric circles. The radius (in feet) of the outer is described by the equations r = 0.5t, where t is time (measured in seconds after the pebble strikes the water). The area of the circle is given by the function A(r)= πr^2. Find and interpret(explain what the answer means) (A○r)(t).