A credit card company operates two customer service centers: one in Boise and one in Richmond.Callers to the service centers dial a single number,and a computer program routs callers to the center having the fewest calls waiting.As part of a customer service review program,the credit card center would like to determine whether the average length of a call (not including hold time) is different between the two centers.The managers of the customer service centers are willing to assume that the populations of interest are normally distributed with equal variances.Suppose a random sample of phone calls to the two centers is selected and the following results are reported: 
Using the sample results,develop a 90% confidence interval estimate for the difference between the two population means.
Definitions:
Efficiency Wages
Wages set above the market equilibrium by employers to boost employee productivity, morale, and loyalty, and to reduce turnover.
Discriminatory Wage Differentials
Variation in wages among workers that arises from factors unrelated to skills or job performance, often based on race, gender, ethnicity, or other non-performance related characteristics.
Customers
Individuals or businesses that purchase goods or services provided by a company or a store.
Market Forces
The supply and demand mechanisms that determine the price and quantity of goods and services in a free market.
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