In any operating system such as industries, factories or any system which involves job performing units such as machines, tools, men etc. faces a replacement problem whenever these job performing units become less effective or obsolete due to gradual deterioration in their efficiency or sudden breakdown. For example in a corporate office the computer stops working all of a sudden or some employees need to be replaced as not being skilled up to date. In a factory of wafers the packing machine stops working or a air conditioner fails to work or gas pipelines gets blocked. These are some situations when the operating system needs a cost efficient replacement rule to replace the faulty units or to find some remedies to regain the efficiency.