A travel agent wants to determine how much the average client is willing to pay for a weekend at an all-expense paid resort. the agent surveys 30 clients and finds that the average willingness to pay is $2,500 with a standard deviation of $840. however, the travel agent is not satisfied and wants to be 95% confident that the sample mean falls within $150 of the true average. what is the minimum number of clients the travel agent should survey? note that z=1.96 for a 95% confidence interval. please give your answer as an integer with no decimal point and no digits to the right of the decimal point.