High blood pressure (hypertension) is a common condition in which the long-term force of the blood against your artery walls is high enough that it may eventually cause health problems, such as heart disease.Thedistribution of blood pressure of a certain population has anormal distribution with mean120mmHg and standard deviation50

50mmHg. Asimple random sample of size81

81is obtained from the population.

What is the probability that the mean blood pressure forthe81 (81individuals is between118)

A blood pressure of165mmHg or above is considered to be "unusually high''. Find the approximation to the probability that atleast15of the 81individuals have "unusually high'' blood pressure.