Armer Company is accumulating data to use in preparing its annual profit plan for the coming year. The cost behavior pattern of the maintenance costs must be determined. The accounting staff has suggested the use of linear regression to derive an equation for maintenance hours and costs. Data regarding the maintenance hours and costs for the last year and the results of the regression analysis follow: Maintenance Month Cost Jan. $ 4,700 Feb. 3,500 Mar. 4,100 Apr. 3,320 May 4,850 June 3,460 July 3,530 Aug. 4,970 Sept. 4,760 Oct. 4,550 Nov. 3,800 Dec. 3,660 Sum $49,200 Average $ 4,100 Average cost per hour a (intercept) b (coefficient) Standard error of the estimate R-squared t-value for b Machine Hours 680 520 600 500 700 510 520 760 690 670 550 540 7,240 $ $ 7.00 603 $ 3.86 6.7892 83.417 0.98383 24.6680 At 400 hours of activity, Armer management can be approximately two-thirds confident that the maintenance costs will be in the range of