Answer:
The Journal entries are as follows:
(a) On January 1, 2020
Cash A/c(6,000 bonds × $102) Dr. $612,000
     To Bonds payable                  $600,000
     To premium on bonds payable       $12,000
(To record the issuance of the bonds)
Workings:
premium on bonds payable = $612,000 - $600,000
                        = $12,000
(b) On July 1, 2020
Interest expense A/c          Dr. $29,700
Premium on bonds payable A/c Dr. $300
    To cash A/c                       $30,000
(To record the interest expense)
Workings:
Cash = $600,000 × (6/12) × 10%
     = $30,000
Premium on bonds payable = $12,000 ÷ 40 periods
                        = $300
(c) On December 31, 2020
Interest expense A/c          Dr. $29,700
Premium on bonds payable A/c Dr. $300
    To Interest payable A/c               $30,000
(To record the accrual of interest expense)