Read the following brief write$-$up and answer the following questions on quality basics. Products used in a sensitive electronic instrument are manufactured to an upper length specification limit of $305\mathrm{.}70$ mm and a lower specification limit of $304\mathrm{.}55$ mm$.$ The products are scrapped if their lengths fall below than the LSL and reworked if greater than USL. The lengths are normally distributed with a mean of $305\mathrm{.}20$ mm and standard deviation of $0\mathrm{.}25$ mm$.$