A system has 6 identical resources and $N$ processes competing for them. Each process can request atmost 2 requests. Which one of the following values of $N$ could lead to a deadlock?

1. 1
2. 2
3. 3
4. 4

My attempt :

Deadlock free condition is :

R <= P(N-1)+1 ,

Where R is total number of resources ,

P is the number of processes , and

N is the max need of each resource .

6 <= P(2-1) + 1 6 <= P + 1 5 <= P

So all options can not be deadlock .

In this exercise problem answer given (4).

What I'm missing here ?