memory hierarchy is composed of an upper level and a lower level.

Data are requested by the processor.

$5$ out of $10$ requests find the data in the upper level and returns the data in $0\mathrm{.}4$ ns$.$

The remaining requests require $1\mathrm{.}4$ ns to return the data.

To $0$ decimal places, what is the miss rate in percent? $($e$.$g$.,$ enter $50$ for a miss rate of $50\%)$