Five online brokers, Fidelity, Scottrade, Charles Schwab, TD Waterhouse, and Ameritrade must distribute amongst themselves 100 shares of  the world’s most expensive stock listed on any market in the world : Berkshire Hathaway Inc. (NYSE:BRK.A)

The online brokers have committed to a strict order of seniority:
Ameritrade is superior to Charles Schwab, who is superior to Fidelity, who is superior to TD Waterhouse, who is superior to Scottrade.

The online brokers also follow strict rules of shares distribution, which are : the most senior online broker should propose a distribution of shares.
The online brokers, including the senior broker, then vote on whether to accept this distribution.
If the proposed allocation is accepted by a majority vote, it happens.
If not, the proposer must resign, and the next most-senior online broker makes a new proposal to begin the system again.

In the event of a tie vote, the most senior online broker has the casting vote.

Online brokers base their decisions on three factors, in order of priority:
First of all, each online broker does not want to resign.
Second, each online broker wants to maximize the number of shares he receives.
Third, all things being equal, a broker would prefer to force the most-senior broker to resign.

Question : What is the number of shares each online broker receives?