Consider a $6-$stage pipeline with stage delays of $35,40,28,42,30$ and $38$ nanoseconds respectively. If the latch delay in each stage is $5$ nanoseconds, what is the maximum clock frequency with which the pipeline can operate?

a$)21\mathrm{.}3MHz$

b$)20\mathrm{.}2MHz$

c$)18\mathrm{.}6MHz$

d$)$ None of these