An equation was used to predict possible sales of phones for 6 months. The actual sales of phones are also listed.
Actual sales
55 150 325 510 780 990
Predicted sales
40 150 300 500 800 1,000
The sum of the residuals is ______.
Actual sales
55 150 325 510 780 990
Predicted sales
40 150 300 500 800 1,000
The sum of the residuals is ______.