4.34375 would be the approximate answer.
Answer: 0.965
Step-by-step explanation:
Given : Water use in the summer is normally distributed with


Let X be the random variable that represents the quantity of water required on a particular day.
Z-score : 

Now, the probability that a day requires more water than is stored in city reservoirs is given by:-

We can see that on comparing the above value to the given P(X > 350)= 1 - P(Z < b) , we get the value of b is 0.965.
It is less than. Any negative number compared to a positive number will be less than.