c. For the age group 40-59, what is the probability of ending up in Intensive Therapy for each of the three categories (not-vaccinated, partially vaccinated, fully vaccinated)? [Example: what is the probability of ending up in Intensive Therapy, conditional on being a 40-59 non-vaccinated?]

If the probability of getting selected for each outcome is equal then such outcomes can be termed as equally likely outcomes. For equally likely outcomes, the probability of favorable event can be given by dividing the number of favorable outcomes, with the total number of outcomes.
                                   $Probability of favorable event=\frac{Number of favorable outcomes}{Total number of outcomes}$

The conditional probability of happening of event A when event B already happened, can be expressed as, $P\left(A\overline{)B}\right)$.