A bank manager wants to know the mean amount of mortgage paid per month by homeowners in an area. A random sample of 117 homeowners selected from this area showed that they pay an average of $1583 per month for their mortgages. The population standard deviation of such mortgages is $216. a. Find a 95% confidence interval for the mean amount of mortgage paid per month by all homeowners in this area. Round your answers to two decimal places. i dollars b. Suppose the confidence interval obtained in part a is too wide. Select all of the ways the width of this interval can be reduced. O Lowering the confidence level O Increasing the confidence level O Increasing the sample size O Lowering the sample size