11. (8 points) Listed below are costs (in dollars) of airfare from New York to San Francisco, based on tickets purchased 30 days or one day in advance. 30 Days 244 260 264 264 278 318 280 One Day 456 614 567 943 628 1088 800 a) Find the linear correlation coefficient r using a calculator. b) At a 0.05 significance level, is there evidence of a linear correlation between costs of tickets purchased 30 days in advance and those purchased one day in advance? Justify your answer using either the P-value or critical value method. c) Write the least squares regression equation. d) If the cost of a ticket purchased 30 days in advance is $300, predict the price if purchased one day in advance