Merril lynch Securties and Health Care Retirement inc, are two large employers in downtown Toledo, Ohio. They are considering jointly offering child care for their employees. As a part of the feasibility study, they wish to estimate the mean weekly child care cost of their employees with 95% confidence. Based on a previous study, the standard deviation of the weekly child-care is $5.7. How large a sample is needed to keep the margin of error as small as $0.5?