=+8" Silk plc invests surplus cash in a range of money-market securities which earn a rate of return of 8 per cent per annum. It tries to hold the smallest cash balances possible while permitting the business to operate. For the next year there will be a need for cash taken from near-cash investments (money market investments) of £40,000 per week. There is a fixed cost of liquidating these securities of £200 regardless of amount (a combination of broker's fees and administration costs). Should Silk draw on these funds every week or at some other interval? Calculate the optimum level of cash balance.