**Q470.** This is one of a series of problems (469, 471, 472, 473, 474, 475, 476, 477, 478) relating to the same fictional case: The community of Ourville which is considering some options for creating parks to enhance the quality of life of local residents. The amounts are expressed in simple numbers – e.g., $100 – which you can assume to be referring to realistic amounts – e.g., hundreds of thousands.

One part of the staff report talks about discounting. A resident asks "where do discount rates come from?" Your (BRIEF) answer:

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**Difference Equations** DE01 notation | DE02 text2eqns | DE03 pn+1 chart | DE04 excel | DE05 de-and-etc | DE06 caveats |

**Flow Chart** FC01 text2chart | FC02 stepwise-refine | FC03 time-dol | FC04 diagnose | FC05 software | FC06 caveats |

**Decision Tree** DT01 probability | DT02 emv | DT03 text2chart | DT04 simple-tree | DT05 val-of-info | DT06 risk | DT07 imperfect-test | DT08 utility | DT09 concepts-terms | DT10 caveats |

**Cost Benefit** CBA01 basic-idea | CBA02 compute-nb-mb | CBA03 four-scenarios | CBA04 workflow | CBA05 concepts-terms | CBA06 caveats |

**Discounting** D01 basic-idea | D02cmpnd-int | D03 compute-NPV | D04 whence-DR | D05 curves | D06 concepts-terms | D07 caveats |

**Stock-n-Flow** SF01 concepts-terms | SF02 text2loop | SF03 text2sf | SF04 sf2de | SF05 describe-systems | SF06 software | SF07 caveats |

**Markov** MM01 general-idea | MM02 system-prereqs | MM03 text2matrix2diagram | MM04 2excel | MM05 concepts-terms | MM06 caveats |

**Linear Programming** LP01 concepts-terms | LP02 text2ineqalities | LP03 solve-graphically | LP04 excel | LP05 caveats |