A new product just came onto the market and is a big hit. The success, however, does not last long. Within a year, sales/day have dropped drastically. Given that the number of sales/day, measured in tens of thousands, of the product is represented by the function n(t) = -50(e-4t-e-3t) after t years, w is the day that the most products are sold? How many products were sold on that day? (5 marks)