**Table 3. The regression coefficients and probability (p-value) or corresponding response**

| Total peak area (Y_{1}) | D-Limonene (Y_{2}) |

Coefficient | p-value | Coefficient | p-value |

Intercept | 1,154.55 | <0.0001 | 633.7046 | <0.0001 |

X_{1} | –9.19 | 0.5381 | –4.2584 | 0.5273 |

X_{2} | 157.35 | <0.0001 | 91.4329 | <0.0001 |

X_{3} | –14.90 | 0.3389 | –13.219 | 0.0922 |

X_{1}X_{2} | 10.60 | 0.6126 | 16.3703 | 0.1238 |

X_{1}X_{3} | –23.00 | 0.2942 | –9.939 | 0.3127 |

X_{2}X_{3} | 35.17 | 0.1293 | 18.9825 | 0.0885 |

X_{1}^{2} | –41.36 | 0.0952 | –12.8638 | 0.2159 |

X_{2}^{2} | –127.38 | 0.0017 | –68.3523 | 0.0008 |

X_{3}^{2} | 51.36 | 0.0562 | 37.6797 | 0.0101 |

Model | | 0.0021 | | 0.0006 |

R^{2} | 0.9248 | 0.9537 |