Your current sales consist of $25$ units per month at a price of $$200$ a unit. You are weighing the pros and cons of switching to a net $30$ credit policy from your current cash only policy. If you decide to switch your credit policy you also plan to increase the sales price to $$215$ a unit. The monthly interest rate is $2$ percent. What is the break$-$even default rate of the proposed switch?Question

options:

$4\mathrm{.}48$ percent

$4\mathrm{.}59$ percent

$4\mathrm{.}65$ percent

$4\mathrm{.}97$ percent

$5\mathrm{.}12$ percent