This excerpt taken from the GBTB DEF 14A filed Apr 10, 2006.
Exercise of Options. Subject to earlier termination of the option as provided herein, unless the Board determines otherwise, options will be exercisable from the date and after the date of grant. Vesting or other restrictions on the exercisability of an option will be set forth in the related Option Agreement.
All or any part of the exercisable portion of an option may be exercised at any time during the option period. An option may be exercised by transmitting to the Bank (1) a written notice specifying the number of shares to be purchased, and (2) payment of the exercise price in cash or by certified or cashiers check or
by such other means or in such other manner of payment as the Board may permit, together with the amount, if any, deemed necessary by the Board to enable the Bank to satisfy its income tax withholding obligations with respect to such exercise (unless other arrangements acceptable to the Bank are made with respect to the satisfaction of such withholding obligations).