What a profitability tree is
A profitability tree decomposes Profit = Revenue − Cost into ever-finer drivers, so you can isolate exactly where a profit problem comes from. Revenue branches into price and volume; cost into fixed and variable. It's the most common structure in case interviews because it's naturally MECE.
How to use it in a case
Start from Profit = Revenue − Cost, branch each side into its drivers, then ask which branch the data points to. Drill only the branch that matters instead of analyzing everything. Build your tree above — it saves automatically in your browser.