Assume a memory access to main memory on a cache "miss" takes $30$ ns and a memory access to the cache on a cache "hit" takes $3$ ns$.$ If $80\%$ of the processor's memory requests result in a cache "hit", what is the average memory access time?

Select one:

a$.8\mathrm{.}4ns$

b$.33ns$

c$.2\mathrm{.}4ns$

d$.24\mathrm{.}6ns$

e$.27ns$