0.001657 - 0.07586 \chi_- + 0.1762 \eta \chi_+ + 1.358 \eta \chi_- + 0.1103 \chi_+^2 + 0.1361 \chi_-^2 - 0.03407 \eta^3 - 2.147 \eta^2 \chi_+ - 7.814 \eta^2 \chi_- - 1.334 \eta \chi_+^2 - 1.295 \eta \chi_-^2 - 0.09387 \chi_+^3 - 0.01674 \chi_+ \chi_-^2 + 5.87 \eta^3 \chi_+ + 14.41 \eta^3 \chi_- + 3.323 \eta^2 \chi_+^2 + 2.948 \eta^2 \chi_-^2 + 0.1427 \eta \chi_+^3 - 0.03698 \chi_+^4