The revenue function is .

Monthly selling cost function is

(a).

How many wrist watches to sell for maximum revenue.

The revunue is .

The general form of quadratic equation is .

Consider the two equations , .

Vertex is

Axis of symmetry

.

To obtain maximum revenue,the shopkeeper must sell boxes.

The maximum revenue is

The maximum revenue is  dollars.

Therefore to obtain maximum revenue dollars, the shopkeeper must sell boxes.

(b).

The profit function is .

Substitute and .

The profit function is 

(c).

How many watches to sell to maximum profit?

The function is  .

The general form of quadratic equation is .

Consider the two equations , and

Vertex is

Axis of symmetry

.

To obtain maximum profit, the shopkeeper must sell boxes.

The maximum profit  is

The maximum profit is  dollars.

Therefore to obtain maximum profit dollars, the shopkeeper must sell boxes .

(a)To obtain maximum revenue dollars, the shopkeeper must sell boxes.

(b) The profit function is .

(c).To obtain maximum profit dollars, the shopkeeper must sell boxes .