The February Revolution had toppled Tsar Nicolas II of Russia, and replaced his government with the Russian Provisional Government. However, the provisional government was weak and riven by internal dissension. It continued to wage World War I, which became increasingly unpopular. A nationwide crisis developed in Russia, affecting social, economic, and political relations. Disorder in industry and transport had intensified, and difficulties in obtaining provisions had increased. Gross industrial production in 1917 had decreased by over 36% from what it had been in 1914. In the autumn, as much as 50% of all enterprises were closed down in the Urals, the Donbas, and other industrial centers, leading to mass unemployment. At the same time, the cost of living increased sharply. Real wages fell about 50% from what they had been in 1913. Russia's national debt in October 1917 had risen to 50 billion rubles. Of this, debts to foreign governments constituted more than 11 billion rubles. The country faced the threat of financial bankruptcy.

Based on the above article, answer a question. How many billion rubles of debt were not owed to foreign governments?
39