Rate of change in cost and revenue

Let 'p' be the price per unit of a certain product, when there is a sale of 'x' units. The total revenue function is : P(x)=(100x)/(3x+1)-4x. (i) Find the marginal revenue function, rate of change of total revenue function with respect to x. (ii) When x = 10, find the relative change of revenue R, i.e., Rate of change of R with respect to x and also the percentage rate of change of R at x=10.

If the rate of change of sine of an angle theta is k, then the rate of change of its tangent is

Matching Of Cost And Revenue