Interest income and/or rental income earned by one Canadian-controlled private corporation may be treated as specified investment

Question:

Interest income and/or rental income earned by one Canadian-controlled private may be treated as specified investment business income. At the same time, income from the same source(s) earned by another Canadian-controlled private may be treated as active business income. Why is this? And to what extent will the rate of tax applied to that income be different for the two corporations?
Corporation
A Corporation is a legal form of business that is separate from its owner. In other words, a corporation is a business or organization formed by a group of people, and its right and liabilities separate from those of the individuals involved. It may...