The amount of photosynthesis that takes place in a certain plant depends on the intensity of light x according to the equation f(x)=145x^2-30x^3 (i). Find the rate of change of photosynthesis with respect to the intensity.
(ii). What is the rate of change when 1? x  when 3? x 
(iii). How fast is the rate found in part (a) changing when 1? x  when 3? x 