26. Find the least positive residue of
a) $3^{10}$ modulo 11
b) $2^{12}$ modulo 13
c) $5^{16}$ modulo 17
d) $3^{22}$ modulo 23 .
e) Can you propose a theorem from the above congruences?
26. a) 1 b) 1 c) 1 d) 1 e) $a^{p-1} \equiv 1(\bmod p)$ when $p$ is prime and $p \nmid a$