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.