A processor of carrots cuts the green top off each carrot, washes the carrots, and inserts six to a package. Twenty packages are inserted in a box for shipment. To test the mass of the boxes, a few were checked. The mean mass was 9.2 kg, the standard deviation 0.27 kg. How many boxes must the processor sample to be 99% confident that the sample mean does not differ from the population mean by more than 0.14 kg?

Can you show me how to get the sample size? step by step process