Even though the sample model coefficient for machine hours (see part b) appears to be considerably different from the hypothesized value of $1,100, the hypothesis test demonstrated that the population model coefficient (the true marginal cost for all months) is NOT significantly different from $1,100. Furthermore, the confidence interval supported the hypothesis test results by showing that the true marginal cost for all months may be as low as $ (Lower Bound), therefore the hypothesized value of $1,100 is certainly plausible.