$2.$ Identify, with reasons, the most appropriate data structure for each of the following cases:

$($i$)$ The bank teller retrieves the account details of customers using their account number.

$($ii$)$ An ambulance dispatch system assigns its emergency response teams to patients presenting the most severe symptoms first.

$($iii$)$ To identify the next passenger to come forward to unload his$/$her baggage from a coach $($bus$)$ storage area.

$3.3.$ For each of the following operations, indicate the worst$-$case run time for a list of size n$.$ Your answer should be written in Big$-$O notation.

i$.$ Finding the size of a singly linked list without a size field

ii$.$ Finding the size of a doubly linked list without a size field

iii. Getting the last element of a doubly linked list

iv$.$ Searching for a value in a sorted doubly linked list

v$.$ Getting an element at a particular index of singly linked list