a) Find the area under the normal curve to the left of z= -3 plus the area under the normal curve to the right of z=3
2) Assume that the random variable X is normally distributed, with mean μ=42 and standard deviation σ=7. Compute the probability. P(x≤ 39)=?
3)Assume the random variable X is normallydistributed, with mean μ=55 and standard deviation sigma σ equals=8. Find the 9th percentile