Answer:
$23
Explanation:
ABC will sell based the lowest bid starting from the highest bid until all the 1,000 shares are allotted downwards as follow:
Number shares to bid of $26 for 100 shares = 100 shares
Number shares to bid pf $25 for 200 shares = 200 shares
Number shares to Alex's bid of $24 for 500 shares = 500 shares
Number shares to bid of $23 for 600 shares = 200 shares
Under Dutch auction, the lowest bid price of all the allotted or successful  bidders will be paid by all the successful bidders.
Since the $23 is the lowest successful bid price, Â Alex ad to pay $23 for each share he obtained