A 2008 survey of low- and middle-income households conducted by Demos, a liberal public group, showed that consumers aged 65 years and older had an average credit card debt of $11,535 and consumers in...

I need the solution for (d) please

Extracted text: A 2008 survey of low- and middle-income households conducted by Demos, a liberal public group, showed that consumers aged 65 years and older had an average credit card debt of $11,535 and consumers in the 50- to 64-year age group had an average credit card debt of $10642 at the time of the survey (USA TODAY, July 28, 2009). Suppose that these averages were based on random samples of 1000 and 1200 people for the two groups, respectively. Further assume that the population standard deviations for the two groups were $2200 and $2500, respectively. Let µ1 and µ2 be the respective population means for the two groups, people aged 65 years and older and people in the 50- to 64-year age group. (a) What is the point estimate of u1- µ2? (b) Construct 98% confidence interval for u1 – µ2 and interpret the results. (c) What is the margin of error? (d) Conduct the appropriate two-tailed test at 5% level of significance.