In a study conducted by the Water Resources Center, two different wastewater treatment plants are compared. Plant A is located where the median household income is below $40,000 a year, and plant B is located where the median household income is above $60,000 a year. The amount of wastewater treated at each plant (thousands of gallons/day) was randomly sampled for 10 days. The data are as follows:

Plant A:

21 19 20 23 22 28 32 19 13 18

Plant B:

20 39 24 33 30 28 30 22 33 24

Can we conclude, at the 2% level of significance, that the average amount of wastewater treated at the plant in the high-income neighborhood is more than that treated at the plant in the low-income area? Assume approximate normality.