(c) 541039, 12181710, 793451, 68888 12. From the digits 2, 5, 1, 0, 9 make any four 8-digit numbers using each digit at least once. Arrange them in descending order. 13. Seven billion three hundred million one hundred thousand eight in figures is (A) 730,001,008 (B) 7,300,001,008 (C) 7,300,100,008 Na One hillion is equal to (D) 7,300,101,008​