Answer:
23rd January 2018
Dr Common share 600
Cr Cash 600
(to record the repurchase of 20 million common shares at $30)
3rd September 2018
Dr Cash 93
Cr Common Share 90
Cr Paid-in Capital 3
(to record the sold of 3 million common shares at $31, thus get $31 x 3 million =93 million increase in Cash, in which $30 x 3 million = $90 million will be credited to Common share account ( as reacquired price is $30 per share), the other $3 million will be credited to Paid-in capital account)
4th November 2018
Dr Cash 84
Dr Paid-up capital 3
Dr Retained earnings 3
Cr Common share 90
(to record the sold of 3 million common shares at $28, thus get $28 x 3 million =84 million increase in Cash. Common share account will be credited at the amount of $30 x 3 million = $90 million( as reacquired price is $30 per share), leaving $3 million will be debited to Paid-in capital account ( available balance) and another $3 million will be debited to Retained earnings).
Explanation:
Explanations are given in each entry.