+407 1) What is the smallest positive integer n such that the rightmost three digits of n! and (n+1)! are the same?
2) \(N=1991\cdot1993\cdot1995\cdot1997\cdot1999. \) What is the sum of the hundreds, tens and units digits of N?
3) What is the remainder when \(2+4+6+\cdots+100 \) is divided by 7?
