Olivia purchased dress shirts to sell in her clothing store that has overhead expenses equal to $15\mathrm{.}00\%$ of costs. To make a profit of $16\mathrm{.}00\%$ of the cost, she sells them at a regular price of $$65\mathrm{.}00$ each.

a$.$ What rate of markdown is required to sell the shirts at break$-$even?

$\%$

Round to two decimal places

b$.$ What rate of markdown is required to sell the shirts at cost$?$

$\%$