Answer:
1. The maturity value is $300,000
2. The carrying amount of the bonds is at December 31, 2018 is $264,000
3.  Semiannual cash interest payment on the bond = $300,000 * 5% * 1/2 = $7,500
4. Discount on BP = $300,000 * 15% = $45,000
Straight line method amortization = $45,000 / ( 10*2 = 20) = $2,250
Interest Expenses = $7,500 + $2,250 = $9,750
Journal Entry                          Debit          Credit
Interest Expenses                 $9,750  
Discount on Bond Payable                      $2,250
Cash                                                           $7,500