2. [24 points] In a real computer system, neither the resources available nor the demands of threads for resources are consistent over long periods (months). Resources break or are replaced, new processes and threads come and go, and new resources are bought and added to the system. If deadlock is controlled by the banker's algorithm, which of the following changes can be made safely (without introducing the possibility of deadlock), and under what circumstances?

a. Increase Available (new resources added).

b. Decrease Available (resource permanently removed from system).

c. Increase Max for one thread (the thread needs or wants more resources than allowed).

d. Decrease Max for one thread (the thread decides it does not need that many resources).

e. Increase the number of threads.

f. Decrease the number of threads.