We start with $10,000, but by putting profits back into the business we could make an arbitrarily large number of computers over time, in theory.
Assuming that we do not put any profits back into the business, it is unclear why we are told that the demand for laptops is three times that of desktops. Are we expecting that we might make some computers that we are unable to sell?
If we assume additionally that every computer we make will be sold, then I think it's pretty clear that the way to maximize profits is to make 25 laptops and 0 desktops, for a profit of $7,500. But that answer seems too simple.
If we are allowed to put profits back into the business but are limited to 90 hours total work, then any combination of laptops and desktops which uses up all 90 hours will result in the maximum profit of $9,000 -- again, assuming that all computers are sold.
I'm really not sure what the person who made the problem was trying to ask.