During routine conversations, the CEO of a new start-up reports that 22% of adults between the ages

Question:

During routine conversations, the CEO of a new start-up reports that 22% of adults between the ages of 21 and 39 will purchase her new product. Hearing this, some investors decide to conduct a large-scale study, hoping to estimate the proportion to within 4% with 98% confidence. How many randomly selected adults between the ages of 21 and 39 must they survey?