What is the difference for rTSR between Stretch and Entry?
{"Entry": {"rTSR": 16.66, "SALES/SQM": 6.66, "ROFE": 6.66}, "Target": {"rTSR": "n/a", "SALES/SQM": 20.0, "ROFE": 20.0}, "Stretch": {"rTSR": 33.33, "SALES/SQM": 33.33, "ROFE": 33.33}}
stretch_rTSR = df["Stretch"]["rTSR"]
entry_rTSR = df["Entry"]["rTSR"]
answer = stretch_rTSR - entry_rTSR