AFMLimni Co (Jun 13) - additional taxation rate (why 6% and not 7.5%)?

Limni Co says that $15 million in dividends was received from overseas subsidiaries on which 20% tax was already paid. 26% is the rate in Limni's jurisdiction with credit given for tax already paid. Wouldn't this mean that $15 million is 80% of the amount on which the tax was levied, so the dividends actually paid was $15/08 million = $18.75 million? 26% of this amount would be $4.875 m. The tax already paid on it was $18.75 m - $15 m = $3.75 m. Thus, it seems to me that the tax still due in Limni's jurisdiction would be $4.875 m - $3.75 m = $1.125 m. Or to put it simply, the tax still due from the $15 million is 0.06/0.8 = 0.075 or 7.5%. If the tax in Limni's jurisdiction is charged on the amount actually received i.e. $15 m, then the tax due would be 26% of $15 m = $3.9 million and the tax already paid would still be $15 m x 0.2/0.8 = $3.75 million, so the tax still due would be $3.9 m - $3.75 m = $0.15 m i.e. 26% - 0.2/0/8 = 1%. I don't understand why in the examiner's answer the additional tax is the difference in tax rates applied to the after-tax amount from the subsidiary i.e. 6% of $15 m, which is $0.9 m.