Suppose that for a company manufacturing calculators, the cost, and revenue equations are given by $$C=70000 + 30 x, \qquad R=200 - \frac{x^2}{40},$$ where the production output in one week is $x$ calculators. If the production rate is increasing at a rate of 500 calculators when the production output is 6000 calculators, find each of the following:

Rate of change in cost =

Rate of change in revenue =

Rate of change in profit =