You are considering adding a new food product to your store for resale. You are certain that, in a month, the minimum demand for
the product will be 6 units while the maximum demand will be 8 units. The estimated demand for this new product in any given month is 6 units (p=0.1), 7 units(p=0.4), and 8 units(p=0.5). If you choose to purchase 7 units for resale this month, what is the probability of selling all 7 units?