Steps:

1. Turn on your computer

2. Select STAT (the second button in the third row represents statistics).

3. Select 1. edit

4. Substitute the value of x into the value of L 1 y into L2.

Get a table like this

L 1 L2

0 15000

1 13000

2 10900

5 3000

5. Click STAT again, move one square to the right to CALC, select 4:LinReg(ax+b), and then confirm that the computer will calculate the least square linear regression for you.

The equation obtained from the problem table is y =-2428.5438+0x+15332.438+042.

6. The problem is that x=4, then substitute 4 to get 56 17.858. The answer is C.