If sales are $$400,000,$ variable costs are $80\%$ of sales, and operating income is $$40,000,$ what is the operating leverage?

a$.$

$7\mathrm{.}5$

b$.$

$2\mathrm{.}0$

c$.$

$0\mathrm{.}0$

d$.$

$1\mathrm{.}3$