Suppose that there are $27489525$

items with which each item is required to be labelled with a unique number. In each answer box below, provide the answer in the form of an integer without any white spaces.

$($a$)$ If each item is to be labelled with a N$-$bit word, what is the minimum value of N$?$

$25$

$25$

$($b$)$ If each item is to be labelled with a hexadecimal value with a fixed length of P nibbles, what is the minimum value of P$?$