Most of the following are investing activities for Banff Inc. Which is NOT an investing activity for Banff Inc. ?

a. Using idle cash, Banff purchases 10-year bonds issued by Mayfair Inc.

b. Banff sales construction equipment, which it had used for the past 8 years in normal operations

c. Banff purchases of a new office building for use by Banff employees

d. Banff issues shares of Banff preferred stock to shareholders in exchange for cash