A fir tree takes 10 years to reach adult size. We want to estimate the average size of a 4-year-old tree. Suppose that the size (in cm) of a 4-year-old fir tree is normally distributed. A random sample of 20 4-year-old fir trees gave a sample mean of 25.25 cm and a sample standard deviation of 4.5 cm. This sample also gave a confidence interval of width 2.673. We select a second random sample of at least 40 fir trees that gave a sample standard deviation of 5.6 cm and construct a confidence interval for using the same confidence level as in the first interval. This new confidence interval is of width 2.186. What is the size of the second sample