Boris plc has 1,000,000 extra cash and the management of the firm must choose between investing the cash in preferred stock that yields 10% per annum or paying the cash out as a dividend to investors who would then invest in the preferred stock themselves. The corporate tax rate is 28% and there is a dividend exclusion of 70% that applies to corporations. (In other words, 70% of dividends received from another corporation are tax-free.) What personal tax rate (a single one applicable to any type of income) will make the stockholders indifferent to the outcome of the company's dividend decision? Support your answer by showing the relevant calculations.