$6.$ Determine the high temperature performance grade required for a pavement placed at a toll station $($i$.$e$.,$ where there will be standing traffic$)$ that needs to withstand $4$ million ESALs. The weather station information for the location where the pavement will be placed are given in the table below. Use a reliability of $98$ percent when selecting the appropriate grade.

$($a$)$ PG $52$

$($b$)$ PG $58$

$($c$)$ PG $64$

$($d$)$ PG $70$