The articles of incorporation of X Corporation, a construction company, classify its shares into voting common stock and non-voting preferred stock, and provided for 11 directors. Its by-laws, on the other hand, give the board of directors the authority to approve transactions not exceeding P2, 000,000.00. Any transactions in excess of the said amount have to be ratified by the stockholders. In which of the following cases may the preferred stock vote?

a.Approval of a loan amounting to P3, 000, 000.00 from Banco De Oro

b.Declaration of stock dividends from the unissued common stock

c.Increase in the number of directors from 11 to 15

d.Purchase of cement worth P2, 500, 00.00 from Davao Cement Corporation

Choose the correct letter and explain your answer.