Niagara Dairies gives convenience stores a trade discount of $20\%$ on butter listed at $$86$ per case. What rate of discount will Silverwood Milk Products have to give on its list price of $$89\mathrm{.}50$ per case to match Niagara$$s price to convenience stores? $($Do not round intermediate calculations and round your final answer to $2$ decimal places.$)$

Discount rate