Answer:
Given :The monthly demand for a product is normally distributed with mean = 700 and standard deviation = 200.
To Find :
1. What is probability demand will exceed 900 units in a month?
2. What is probability demand will be less than 392 units in a month?
Solution:

We are supposed to find probability demand will exceed 900 units in a month.
Formula : 
We are supposed to find P(Z>900)
Substitute x = 900


Refer the z table.
P(Z<900)=0.8413
P(Z>900)=1-P{(Z<900)=1-0.8413=0.1587
So, the probability that demand will exceed 900 units in a month is 0.1587.
Now we are supposed to find probability demand will be less than 392 units in a month
We are supposed to find P(Z<392)
Substitute x = 392


refer the z table
P(Z<900)=0.0618
So, probability that demand will be less than 392 units in a month is 0.0618.