If substantially all of the assets of the permanent university fund are invested in an internal investment fund established by the board of regents of The University of Texas System, the cost value of the permanent university fund’s investment in the commingled fund for the purpose of Sections 18(a) and (b), Article VII, Texas Constitution, shall be calculated by multiplying the permanent university fund’s ownership percentage in the commingled fund by the commingled fund’s net asset value at cost as determined by the board of regents. The permanent university fund’s ownership percentage of the commingled fund shall be determined by dividing the permanent university fund’s units of participation or shares by the total units or shares of the commingled fund.