(a).

Draw the coordinate plane.

Plot the points.

Graph :

(b).

From the cubic regression method the polynomial function is

(c).

To find the closing price of stock of the day , graph the function and locate on the graph.

Graph :

Observe the graph :

The price of the stock on day is .

(a).

Graph :

(b).

(c).

Graph :

The price of the stock on day is .