The incubation period for the eggs of a house wren is normally distributed with a mean of 336 hours and a standard deviation of 3.5 hours.

1. Find the probability that an egg has an incubation period between 328 and 338 hours.
2. Suppose a researcher has fifteen house wren eggs in an incubator. Find the probability that the average incubation time for the fifteen eggs is greater than 337 hours.
3. Suppose it is known that 33% of house wren eggs never hatch. Suppose an ornithologist has forty house wren eggs. Find the probability that less than 25% never hatch.