The Bylaws of a Condominium Association provide that the association may alter the size of the board upon $\frac{2}{3}$ vote of the membership. The association is proposing reducing the size of the board from $15$ members to $5$ members. This change would be considered:

a$.$ At a meeting of the board.

b$.$ At an annual meeting when considering the budget.

c$.$ At a special membership meeting by separate vote.

d$.$ At the budget meeting.