A normal population has the mean of50 and the variance of25. A random sample of sizen=51is selected.

(a) Find the standard deviation of the sample mean.

Round your answer to two decimal places (e.g. 98.76).

X=

Enter your answer in accordance to the item a) of the question statement

(b) How large must the sample be if you want to halve the standard deviation of the sample mean?

n=

Enter your answer in accordance to the item b) of the question statement