Specifications for a piece of material used in the manufacture of a bed mattress require that the piece be between a Lower and Upper value $($in inches$)$ centered around the process mean. The process that produces the piece yields a mean of $16$ and a standard deviation of $0\mathrm{.}3$ inches. The distribution of output is normal. Within what values will $85\mathrm{.}33$ percent of sample means fall, if samples of n $=8$ are taken and the process is in control?