Using the $t$ tables, software, or a calculator, estimate the values asked for in parts $($a$)$ and $($b$)$ below.

a$)$ Find the critical value of $t$ for a $90\%$ confidence interval with $df=8?$

$($Round to two decimal places as needed.$)$

b$)$ Find the the critical value of $t$ for a $98\%$ confidence interval with $df=109?$

$($Round to two decimal places as needed.$)$