N= 1!+2!+3!.....+10!. what is the last digit of N^N?  Choose the most appropriate option.
A) 3  B) 4  C) 5  D) 6  E) 7

Rationale: as you see 5 ! till 10 ! each unit digit is zero . so 1 ! + 2 ! + 3 ! + 4 ! = 33 so unit digit 3 + 0 = 3 n = 3 n ^ n = 3 ^ 3 = 27 so last digit is 7 . answer : e
Answer: E