Acompany that makes mobile phones introduces a new, faster model that has strong consumer interest. however, the old model is still available. what will most likely happen to the price of the old model ,and why

The correct answer here would be that the price of the old model would fall in order for people to continue purchasing it.

When a new phone model comes out the most common practice is to reduce the price of the older model in order for it to still be a cheaper alternative for the newer model. That way people with smaller budgets would still buy the products from the same company and it would result in a influx of new costumers.