A taxi company is trying to decide whether to purchase brand A or brand B tires for its fleet of taxis. To estimate the difference in the two brands, an experiment is conducted using 12 of each brand. The tires are run until they wear out. The results are

Brand A:    x̅₁ = 36,300 kilometers,
                   s₁ = 5000 kilometers.
Brand B:    x̅₂ = 38,100 kilometers,
                   s₂ = 6100 kilometers.

Compute a 95% confidence interval for μ_A − μ_B assuming the populations to be approximately normally distributed. You may not assume that the variances are equal.