Answer:
12,338,352 companies
Explanation:
If the companies' names can have either 4 or 5 letters, and teh letters can repeat themselves, then the total number of companies that can be listed on NASDAQ is:
4 letter names = 26 x 26 x 26 x 26 = 26⁴ = 456,976
5 letter names = 26 x 26 x 26 x 26 x 26 = 26⁵ = 11,881,376
total number of companies listed = 456,976 + 11,881,376 = 12,338,352