What least number should be subtracted from 642 so that the remainder when divided by 5, 7, and 9 will leave in each case the same remainder 4 ? Pick:
A) 5
B) 6
C) 8
D) 9
E) 10

Rationale: "the lcm of 5 , 7 , and 9 is 315 . the next multiple is 2 * 315 = 630 . 630 + { remainder } = 630 + 4 = 634 , which is 8 less than 642 . answer : c ."
Answer: C