Answer:
- The holding-period return for a one-year investment  :  18%
Explanation:
- The holding period return formula is the next: 
 HPR =   + Income	( +Price Earn	- Price Paid )   /  Price Paid    
It means you have to sum the income of the bond (interest) plus the earning price ( difference Price Ear less Price Paid) , that amount must be divided by the Price Paid. 
In this case the result is: 
-  HPR :  $41,0	+ ( $815,2 - $728,5) /  $728,5 = 127,8/728,5 = 18%  
It's necessary to define the Face value of the bond on both period. 
- At the moment of the purchase it's the present value of the cash flow at the discount rate of  7,1%
  728   YTM 7,1%  
 1  $ 1.000	$ 41
 2  $ 1.000	$ 41
 15  $ 1.000	$ 1.041
- The second price to find it's the Face Value but with one year less of interest and a differente discount rate , in this case, 6,1%.
-  $815,2   YTM 6,1%