Your father just retired with 555,000 TL savings in his private retirement account that pays 0.92% monthly interest. If he wants to withdraw a salary of 6,000TL per month, how long will it take for him to deplete the savings? As a graduate student with excellent knowledge engineering economics, you advice him to be more conservative and withdraw 5,100 TL per month (15% less than his original intention of 6,000 TL). How long will the retirement savings last then? Show your calculations both using analytical formulas and a relevant Excel function. Interpret your findings.