Your bank account consists of a checking and savings accounts. Assume your expenses and earnings can be described by a random walk with an equal probability to spend one dollar or to receive one dollar in your checking account at every time interval. You are charged $5 for any transaction from the checking account to the savings account and viceversa. Also, assume that the cost per unit of cash, per unit of time r of keeping cash on hand is equal to $0.1 dollars for any dollar on hand per time period. Determine: (A) The optimal values of the two thresholds s and S, i. e., the amount of cash in your checking account restored after each transaction, and the maximum amount of cash in your checking account, respectively.