Step by step please

The general manager of a building materials production plant feels that the demand for plasterboard shipments may be related to the number of construction permits issued in the country during the previous quarter. The manager has collected the data shown in the table.

Open table as spreadsheet

Construction Permits	Plasterboard Shipments
15	6
9	4
40	16
20	6
25	13
25	9
15	10
35	16

Use the normal equations to derive a regression forecasting equation.

Determine a point estimate for plasterboard shipments when the number of construction permits is 30.