Here the sample mean is 9.14 mg/l. the population standard deviation of the dissolved oxygen content for the warehouse is known from longexperience to be aboutσ= 2 mg/l.1 (a) find a 98% confidence interval for the unknown population mean dissolved oxygen content.(b) interpret your interval.(c) what sample sizenis required to get a 98% confidence interval with error margin 0.5? (d) to make azconfidence interval, we must assume that the sample mean is (approximately) normallydistributed, which it will be if the population is normal or the sample size is large enough–that is, ifn > 30 by our rule-of-thumb. here we haven= 44, so we do not need to check for a normal population. however, as practice forwhennis smaller, make a normal qq-plot of the sample. is it plausible that the sample came from anormal population?