Not use excel

A net weight control study carried out at a pharmaceutical company that is responsible for the production of liquid medicines (syrups in bottles) suggests a normal distribution with mean of 137.2 oz and standard deviation of 1.6 oz of the contents of jars of a certain type. The declared content was 135 oz. a) What is the probability that a single jar contains more than the declared content? b) Assuming that the mean remains at 137.2, to what value would you have to change the variance such that 95% of all jars contain more than the declared content? c) What content is such that 30% of the jars have contents less than or equal to the same