Ok, for multiplication of fractions you do not need a common denominator so multiply top by top and bottom by bottom... let me know what you get
Each floor is 3.35 feet taller than each floor of the Aon Center
Step-by-step explanation:

this is the answer
The correct answer is the first choice, ($1818.30, $5077.70.)
To find this, we first find the z-score based on the confidence level:
Convert 95% to a decimal: 95%=95/100 = 0.95
Subtract from 1: 1-0.95 = 0.05
Divide by 2: 0.05/2 = 0.025
Subtract from 1: 1-0.025 = 0.975
Using a z-table (http://www.z-table.com) we see that this value is associated with a z-score of 1.96.
Next, we identify

Next we find

Next we find

Next, we multiply this value by z:
1.96(831.479) = 1629.70
The confidence interval is given by