If we know the situation of the first person, we can also calculate the success or failure of the first person according to the conditional probability method, which is similar to the classification description.
But according to your description, it belongs to the first case of not knowing the first person, and it is ok to calculate with the first method of the first case. If you have any questions about this calculation method of directly using 2/5, you can refer to Bayesian formula to help you understand.