Take b = 2.

b^(n-1) mod n = 1.

157 is prime.

b^((n-1)/157)-1 mod n = 2098, which is a unit, inverse 21924.

5 is prime.

b^((n-1)/5)-1 mod n = 15065, which is a unit, inverse 17849.

(5 * 157) divides n-1.

(5 * 157)^2 > n.

n is prime by Pocklington's theorem.