问题如下：
Sam Nakusi is managing a balanced portfolio of fixed income and equity securities worth £1,000,000. The portfolio’s pretax expected return is 6.0 percent. The percentage of return composed of interest, dividends and realized capital gain as well as the associated tax rates are listed below. Assume the portfolio’s cost basis equals market value.
2. In the previous question, recalculate the expected accumulation assuming the portfolio’s costs basis is equal to £700,000.
选项：
A. £1,373,943.
B. £1,962,776.
C. £1,887,776.
解释：
C is correct.
B = £700,000/£1,000,000 = 0.70
FVTaxable = £1,000,000[(1 + r*)n(1–T*) + T*–(0.25)(1–0.70)]
= £1,000,000[(1 + 0.0471)15(1–0.0318) + 0.0318–0.075]
= £1,887,776
这公式最后-0.075是什么意思？