If a pointer is 8 bytes and an integer is 4 bytes, then a ListNode would be 12 bytes in total. The list itself has a pointer to the head of the list (another 8 bytes). The formula then would be 8 + 12 *N to compute the total memory involved for storing a linked list in memory, where N is its size.

What would the formula be for a doubly linked list where there is still no tail pointer?

a.12 + 8 * N

b. 20 + 12 * N

c. 8 + 12 * N

d. 8 + 20*N