Probability by counting

You will write a function for the probability of an event, list the prime numbers on a spinner, and find their chance.

The idea. With equally likely outcomes, $P(E)$ is the number of favourable outcomes divided by the number of all outcomes. Python's Fraction keeps the answer exact.

Your tasks.

1. In probability, return Fraction(len(favourable), len(outcomes)).
2. Set primes to the prime numbers on the spinner, in order.
3. Set p_prime to the probability of a prime, using your function.