Confidence Intervals · Superchallenge problem

A pilot study suggests $s \approx 10$. What is the smallest sample size $n$ for which a $95\%$ $t$ interval has margin of error at most $5$? Use $t^*$ = $2.131$, $2.120$, $2.110$, $2.101$ for $15$, $16$, $17$, $18$ degrees of freedom.