Maria Goeppert was a German physicist. She received the Nobel Prize in Physics in 1963 for the discovery of nuclear orbital structure. She graduated in 1930 using in her thesis the calculus of probabilities to analyse the orbit of the electron.

Now, apply probability to solve the following problem:

There are 50 pupils in a class: 26 are brunettes and 24 are blondes. Three people are chosen at random. Calculate the probability of the following events:

1. All three people are blondes.
2. All three people are brunettes.
3. Exactly two people are blondes.
4. At least two people are brunettes.