The following data have been collected by the controller of Xanthan Corporation over the past 12 months:

Required:
(1) Using the high and low points method, determine the average of fixed maintenance cost per month and the variable maintenance rate per machine hour.
(2) Determine the fixed cost and the variable cost rate, using the method of least squares.
(3) Compute the coefficient of correlation, r, and the coefficient of determination, r2, between the machine hours and the maintenance cost.
(4) Compute the standard error of the estimate.
(5) Determine the 95% confidence interval for maintenance cost at the 2,500-machine-hour level of activity.

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Machine Hours 2,500 2,350 2,000 2,400 2,100 2,600 2,450 2,550 2,700 2,450 2,400 Maintenance Cost Month S 2,200 January February.. March. April.. May June. July. August. 2,130 2,000 2,170 2,050 2,220 2,150 2,250 2,290 2,150 2,210 2.100 $25,920 October.. November.. December. Total 28,800