The chemical composition of soil varies with depth. The article "Sampling Soil Water in Sandy Soils: Comparative Analysis of Some Common Methods" (M. Ahmed, M. Sharma, et al.,Communications in Soil Science and Plant Analysis, 2001: 1677-1686) describes chemical analyses of soil taken from a farm in western Australia. Fifty specimens were taken at each of the depths 50 and 250 cm. At a depth of 50 cm(sample 2), the average NO3 concentration (in mg/L) was 88.5 with a standard deviation of 49.4. At a depth of 250 cm(sample 1), the average concentration was 110.6 with a standard deviation of 51.5. Find a 95% two-sided confidence interval for the difference between the NO3concentrations at the two depths.