A local bakery uses its stock of sugar according to demand for its products. Indeed, the weekly sugar use follows approximately a normal distribution with mean 2,400 lb. and with standard deviation 400lb. The starting supply of sugar is 4,000lb. and there is a scheduled delivery of 2,500lb at the end of each week. Find the probability that, after 12 weeks (including the delivery that comes at the end of the twelfth week), the supply of sugar will exceed 5,000lb (Ignore the very small probability that the sugar runs out completely during this time period.