Distribution of expenses to investment activities shall be made on the same principles as used for subdivision of expenses by major annual statement lines of business. Investment expenses (column [4] of exhibits 2 and 3) shall include all amounts reported as “real estate expenses” (exhibit 2, line 9.1), “investment expenses not included elsewhere” (exhibit 2, line 9.2), and “real estate taxes” (exhibit 3, line 1) and all other costs incurred in connection with the investing of funds, servicing of investments, and the obtaining of investment income, or chargeable against investment income.