Francis gently combed through his hair and four hairs came out. Which is most likely the age of the four hairs?

Hair growth has 3 cycles: anagen (growth of a hair follicle), catagen (intermediate stage of preparation of hair follicles for the resting stage, and deeper hair follicle parts starts to die), telogen (hair shedding stage, older hairs die and shed, new hairs begin to grow).

So the answer to your question is Telogen