Answer:
The net effect of the repurchase and reselling of the common stock will decrease the assets and stockholders' equity.
Explanation:
June 16, 2018 (repurchase of 20,000 stocks)
July 23, 2018 (reselling of 10,000 stocks)
After the repurchase and reselling of the common stock, the total assets decreased by $320,000 (cash account $280,000 - $600,000).
Equity also decreased by $320,000: