basis dual to the symplectic basis $(A^I,B_J)$ of $H_3(M,\zet)$. We choose the intersection numbers to satisfy $$A^I \cap B_J=-B_J \cap A^I = \delta_J^I \qquad{\rm and } \qquad
A^I\cap A^J=B_I\cap B_J=0.$$ The dual cohomology basis is denoted by $(\alpha_I, \beta^J)$ and satisfies $$\eqlabel{basis} \int_{A^J}\alpha_I=\int \alpha_I \wedge \beta^J =
\delta_I^J \qquad{\rm and } \qquad  \int_{B_J} \beta^I=\int \beta^I
\wedge \alpha_J=-\delta_J^I.$$

In terms of this basis the fluxes can be expanded as $$\eqlabel{fluxes}
\begin{split}
H_{RR}&=M_0 \a_0+M_2(\a_1+\a_2+\a_3)
-M_4(\b^1+\b^2+\b^3)-M_6\b^0,\\
H_{NS}&=N_0 \a_0+N_2(\a_1+\a_2+\a_3)
-N_4(\b^1+\b^2+\b^3)-N_6\b^0,\\
\end{split}$$ where the $M_p$’s and $N_p$’s are the flux numbers. Furthermore we take into account that the A-periods of $\Omega$ determine the coordinates on moduli space, while the B-periods determine the derivatives of the prepotential

$$z^I=\int_{A^I} \Omega, \qquad {\cal G}_I(z) = \int_{B_I}
\Omega.$$

In the large complex structure limit the prepotential of the model takes the form [@Candelas] $${\cal G}(z)=-{\frac{1}{3!}} \kappa_{IJK} {\frac{z^I z^J z^K}{z^0}} ,$$ where $\kappa_{IJK}$ are the Yukawa couplings. Since the model can be related to a torus $T^6$ the only non-vanishing Yukawa coupling is $\kappa_{123}=1$ (and symmetric permutations of the indices). The resulting superpotential is $$\begin{split}
W_{RR} &=  -t_1t_2t_3 M_0 + (t_1t_2+t_1t_3+t_2t_3) M_2 + (t_1+t_2+t_3)M_4 + M_6 ,\\
W_{NS} &=  - t_1t_2t_3 N_0 + (t_1t_2+t_1t_3+t_2t_3) N_2 + (t_1+t_2+t_3)N_4 + N_6, \\
