The first year you obtain your Professional Engineer seal, you design and observe construction of 3 small dams, each of which is in a different area of the country. Each of these dams is designed to pass the 25-year storm without overtopping, since they are relatively small and no loss of life or damage to property is likely if they do fail. After that first year, you never design another dam for the rest of your career since you move into management. What is the probability that a) none of the dams will fail over the 35-year period and b) at least one of those 3 dams will be overtopped in your anticipated 35-year career?