It takes a Christmas tree about 10 years to grow from seed to a size ready for cutting. We want to estimate the average height

of a 4-year Christmas tree which has been grown from a seed. Assume that the height of a 4-year tree is normally distributed. A sample of 20 trees has a mean height 25.25 cm and a sample standard deviation 4.5 cm. This sample produces a confidence interval for

of length 2.673. We select a second sample (of at least 40 trees), which has a mean height 27.34 cm and a sample standard deviation 5.6 cm. Based on this second sample, we construct a confidence interval for using the same confidence level as for the firstinterval. This new interval has length 2.186. What was the size of the second sample?