Hartford Steel Corporation is developing a cost function for its manufacturing overhead costs. Data for the past 30 months are given below.

Month Number Overhead Machine Hours Production Runs 1 76667 1772 31 2 73678 1820 22 3 80141 1634 39 4 61985 1006 40 5 72685 1383 39 6 87675 1957 41 7 78450 1561 48 8 70634 1464 34 9 63417 1545 25 10 56057 1119 29 11 67446 1382 35 12 72102 1320 47 13 68533 1264 49 14 69079 1344 29 15 85550 1803 48 16 58197 1022 38 17 61626 1510 21 18 80689 1793 29 19 58256 1149 27 20 55337 1155 22 21 85108 1847 38 22 76485 1832 23 23 67783 1136 42 24 56398 1136 22 25 66622 1330 33 26 63494 1358 26 27 89416 1882 45 28 67518 1174 45 29 73680 1643 31 30 66132 1381 26

(1). Evaluate the possible cost functions using the following criteria, (a) economic plausibility, (b) Goodness-of-fit and (c) individual tests (t tests) for the cost parameters at 95% level of accuracy. Use the following format for the analysis.

). Which model would you recommend and why? (3). For the model with two drivers, predict the overhead cost for 1600 machine hours and 50 production runs. (4). Prepare a 99% confidence interval for the forecast overhead in part (3) above.

Clearly explain with details the confidence interval obtained in (part 4)