you have found an asset with 12.60 percent arithmetic average return and a 10.24

Solution:

In years      Best estimate of return            Working note

5                   12.36%              ((5-1)/(40-1)*0.1024)+((40-5)/(40-1)*0.126)

10                   12.06%             ((10-1)/(40-1)*0.1024)+((40-10)/(40-1)*0.126)

20                    11.45%               ((20-1)/(40-1)*0.1024)+((40-20)/(40-1)*0.126)

The formula for the return on assets is calculated by dividing the net income by the total average assets. The profit margin and total asset sales can also be represented as a consequence of this ratio. For the calculation of the total asset return, either formula may be used.

Opportunity cost of going to college is actually the salary forgone. 
With a yearly salary of $15,000 and a rent of $12000 yearly (parents would not let you live at home), we are left with $15000 - $12000 = $3000 per year 
For 4 years, the opportunity cost will be 4 x $3000 = $12000