Hello!
I would encourage you to give it shot and ask for feedback, that is the best way to learn it ;)
In any case, it´s a classical market sizing, that I would approach the following way:
- Get total country population
- Divide into age groups, since the issue won´t be equally represented among the different groups (e.g., old people will have it much more than young)
- Appply % of sick people - you should ask for this info or some indications-.
Furthermore, if it´s a market sizing exercise in a profitability case, probably you will also need to discriminate, out of the total "sick" population, how many would buy it from you -market penetration-.
Hope it helps!
Best,
Clara