A state politician would like to determine the average amount earned during summer employment by state teenagers during the past summer’s vacation period. She wants a 95.0 % confidence that the sample...

A state politician would like to determine the average amount earned during summer employment by state teenagers during the past summer’s vacation period. She wants a 95.0 % confidence that the sample mean is within
 of the actual population mean. Based on past studies she has estimated the population std. deviation to be about $400. How large should the sample be?