Answer:
99.7% of customers have to wait between 8 minutes to 30 minutes for their food.
Step-by-step explanation:
We are given the following in the question:
Mean, μ = 18 minutes
Standard Deviation, σ = 4 minutes
We are given that the distribution of amount of time is a bell shaped distribution that is a normal distribution.
Empirical Formula:
- Almost all the data lies within three standard deviation from the mean for a normally distributed data.
- About 68% of data lies within one standard deviation from the mean.
- About 95% of data lies within two standard deviations of the mean.
- About 99.7% of data lies within three standard deviation of the mean.
Thus, 99.7% of the customers have to wait:

Thus, 99.7% of customers have to wait between 8 minutes to 30 minutes for their food.
Ans(a):
Given function is 
we know that any rational function is not defined when denominator is 0 so that means denominator x+4 can't be 0
so let's solve
x+4≠0 for x
x≠0-4
x≠-4
Hence at x=4, function can't have solution.
Ans(b):
We know that vertical shift occurs when we add something on the right side of function so vertical shift by 4 units means add 4 to f(x)
so we get:
g(x)=f(x)+4

We may simplify this equation but that is not compulsory.
Comparision:
Graph of g(x) will be just 4 unit upward than graph of f(x).
Ans(c):
To find value of x when g(x)=8, just plug g(x)=8 in previous equation





4x-3x=-1-16
x=-17
Hence final answer is x=-17
Answer:$8.60
I put the work into the picture. Hope this helps!