Answer:
Margin of error = 
Step-by-step explanation:
We are given the following in the question:
Sample size, n = 81
Alpha, α = 0.05
Population standard deviation, σ = 1.2 hours
Margin of error formula:


Putting the values, we get

1/2. 1/6
1/2×3=3/6
3/6+1/6=4/6
4/6=2/3
2/3
Answer:
Total charge = 8.50x + 25.50
Step-by-step explanation:
You multiply the hourly charge($8.50) by the number of hours(x) and add the rental fee($25.50)