The results in the first of the following tables were obtained in a study of the amount of energy metabolized by two similar species of birds under constant temperature. Information based on separate straight-line fits to each data set is summarized in the second table.
a. Plot the least-squares straight lines for each species on the same graph.
b. Test whether the two lines are parallel.
c. Test whether the two lines have the same intercept.
d. Give a 95% confidence interval for the true difference between the mean amounts of energy metabolized by each species at 15°C.

where Ŷi15 is the predicted value at 15°C for species i (i = A, B) and S2Ŷi15 is the estimated variance of Ŷi15 given by the general formula (for X = X0)