Answer:
Disadvantages of Batch Operating System:
- The computer operators should be well known with batch systems.
- Batch systems are hard to debug.
- It is sometime costly.
- The other jobs will have to wait for an unknown time if any job fails.
 
        
             
        
        
        
I’d say monthly. It probably wouldn’t kill you to do it every three months though.
        
                    
             
        
        
        
Using Rule of Addition:
<span>It states that : "The probability that Event A or Event B occurs is equal to the probability that Event A occurs plus the probability that Event B occurs minus the probability that both Events A and B occur."
</span><span>
P(A or B) = P(A) + P(B) - P(A and B)
</span>                 = 0.7 + 0.55 - 0.3
                 = 1.55
        
                    
             
        
        
        
Answer: Systems design 
Explanation: SDLC(Systems Development Life Cycle)  is the cycle that is responsible for the development of the system including several phases related to it.
The system design phase in SDLC works with the physical or hardware units and the logical reports to make a design interface. This phase makes the requirements of the cycle into design and present it for the analysis so that it can test the efficiency of it. 
 
        
             
        
        
        
There is always a risk of you losing files and then you may have to pay for it depending on what services you use.