A new England based commuter airline has taken a survey of 15 terminals and has obtained the following output for the month of February is as follows

Sales( total revenue based on no. of tickets sold in thousand dollars) = 172+25.9*promotion -13.2* competing airline -3.04*free percentage of passengers who flew free

a. Do the passengers who fly free cause sales to decrease significantly. Test Hypothesis.

b. Does an increase in promotions by $1000 change sales by $ 28000 or is the change significantly different from $28000.