For a particular consumer product, the mean dollar sales per retail outlet last year in a sample of n₁ = 10 stores was= $3,425 with s₁ = $200. For a second product the mean dollar sales per outlet in a sample of n₂ = 12 stores was= $3,250 with s₂ = $175. The sales amounts per outlet are assumed to be normally distributed for both products. Estimate the difference between the mean level of sales per outlet last year using a 90 percent confidence interval.