When an interrupt occurs, an Operating System

The correct matching for the following pairs is

(a) Disk scheduling $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$(1) Round robin
(b) Batch processing $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ (2) $$SCAN$$
(c) Time sharing $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ (3) $$LIFO$$
(d) Interrupt processing $$\,\,\,\,\,\,\,\,\,\,\,$$(4) $$FIFO$$

An operating system contains 3 user processes each requiring 2 units of resource R.The minimum number of units of R such that no deadlocks will ever arise is

Each process P_i,i=1.....9 is coded as follows

  Repeat
  P(mutex){
  critical section
  }
  V(mutex)
  Forever

The code for P₁₀ is identical except that it uses V(mutex) in place of P(mutex). What is the largest number of processes that can be inside the critical section at any moment?