(a) 15220 mod 221- 16; (b) 18220 mod 221 and 18110 mod 221 103; (c) 2120 mod 221 1 and 21110 mod 221 220; (d) 103110 mod 221 = 1 and 10355 mod 221 = 103. C L Consider each part (a) to (d) separately. Which parts(s) could be used to show that 221 is composite, without knowing its factors? Give your reasons. (a) 15220 mod 221- 16; (b) 18220 mod 221 and 18110 mod 221 103; (c) 2120 mod 221 1 and 21110 mod 221 220; (d) 103110 mod 221 = 1 and 10355 mod 221 = 103. C L Consider each part (a) to (d) separately. Which parts(s) could be used to show that 221 is composite, without knowing its factors? Give your reasons