According to a 2004 survey by the telecommunications division of British Gas (Source: http://www.literacytrust.org.uk/Database/texting.html#quarter), Britons spend an average of 225 minutes per day...

According to a 2004 survey by the telecommunications division of British Gas (Source: http://www.literacytrust.org.uk/Database/texting.html#quarter), Britons spend an average of 225 minutes per day communicating electronically (on a landline phone, on a mobile phone, by emailing, or by texting). Assume that currently such communication times for all Britons are normally distributed with a mean of 225 minutes per day and a standard deviation of 62 minutes per day. Let
 be the average time spent per day communicating electronically by 20 randomly selected Britons. Find the mean and the standard deviation of the sampling distribution of . What is the shape of the sampling distribution of
?