A marked researcher working for a large shoe retailer wants to estimate the population mean length of customers' feet. He knows from experience that the population is normally distributed with the...

A marked researcher working for a large shoe retailer wants to estimate the population mean length of customers' feet. He knows from experience that the population is normally distributed with the variance. He  wants to develop a 98% confidence interval to estimate this population mean, but he has decided that this margin of error can be no more than ±0.05 units ( total width of the of this interval must be more than 0.05+0.05=0.1)

Determine the size of the sample he would need to collect to obtain this level of precision in his 98% confidence interval for the population mean foot length of customers.