please help asap

1. Let's stretch a little on this one. Assume Shannon's Irish Red sells 1,000 pints per month in the absence of any cannibalization. Assume also that the new Irish Stout will sell 500 pints per month. The relevant price and cost data are: What will be the maximum percentage cannibalization that can exist before the overall change in contribution dollars becomes negative? Express your answer in percentage form to the nearest percent e.g.; 99.49% rounds down to 99%;99.50% rounds up to 100%. Do not include the % symbol