The average utility bill of 55 r/s California households was$88.32 last month. Assume that the s.d. of all Californiahouseholds’ utility bills last month was $12.45. (a) Construct a98% confidence interval for last month’s overall average utilitybill of all California households. (b) The margin of errorassociated with the above c.i. is (c) Interpret the margin of errorin plain language. (d) How large a sample should be selected if wewant the margin of error in (b) to be $2?