$.($a$)$ Suppose a device is forwarding SONET STS$-1$ frames. How much clock drift, as a percentage, on the incoming line would mean that the output payload envelopes must slip backwards by one byte per three physical frames? $|($b$).$ In $6\mathrm{.}2\mathrm{.}2$ SONET it was claimed that sending $2500-$bits required a clock accurate to within $1$ part in $500.$ Describe how a SONET clock might meet the requirement of part $($a$)$ above, and yet fail at this second requirement. $($Hint: in part $($a$)$ the requirement is a long$-$term average$).$