The proportion of buses traveling more than 900 miles would be 0.0485; multiply this by the total number of buses and you will have your answer.
We find the z-score associated with 900 miles:
z = (X - μ)/σ = (900-830.11)/42.19 = 1.66
Using a z-table (http://www.z-table.com) we see that the area under the curve to the left of this, less than this, is 0.9515. This means that the area under the curve to the right of this, greater than this, would be 1-0.9515 = 0.0485.
Answer: His total rental cost will be $164.75.
Step-by-step explanation:
Since we have given that
Cost of per day = $30
Cost of per mile after the first 100 miles = $0.65
According to question, he was travelling 215 miles in 3 days.
So, it becomes,

Hence, his total rental cost will be $164.75.
65.8 + 13.4 = 79 .2. So the answer is c