Answer:
When cumulative voting is used, you are assigned 1 vote per each stock that you own. In this case, since 5 seats are up for election, you will need at least 1/6 + 1 of the total stocks outstanding to be 100% sure that you will be elected to the board of directors. If you have 1/6 + 1 of all the stocks, mathematically it is impossible for you not to elect one board member.
2,567,538 x 1/6 = 427,923, but since you need to be 100% sure, you need 1 more vote = 427,924
if you have 427,924 stocks, then if the remaining 2,139,614 stocks are divided by 5 = 427,922.8 votes, which is less than what you have.