latex equation 大括号

\begin{spacing}{2}
\begin{equation}
\label{Makeq:whole}
  \begin{cases}
  \Delta T=N_{cycle} \times T_{cycle}\\
  N_{cycle} = max(N_{\mu_p} , N_{Tcycle} )\\
  N_{\mu_p} = 4z_{\beta/2}^2\cdot \frac{\displaystyle Var(\mu_p)}{(\displaystyle\varepsilon\cdot \mu_p)^2}\\
  N_{Tcycle} = 4z_{\beta/2}^2\cdot \frac{\displaystyle Var(\mu_p)}{(\displaystyle\varepsilon \cdot T_{cycle})^2}\\
  Var(\mu_p)=(\frac{\displaystyle h^2\cdot T_{on}\cdot \rho}{\displaystyle C(1-\rho)^2})(\frac{\displaystyle h^2\cdot T_{on}\cdot \rho}{\displaystyle C(1-\rho)^2}-1)\\
  Var(T_{cycle})=\frac{\displaystyle h^2 T_{on}^2}{\displaystyle C^2(1-\rho)^2} (1+\frac{\displaystyle h}{\displaystyle PLP\cdot C\cdot(1-\rho)})^2\\
  T_{cycle}=\frac{\displaystyle h^2 \cdot T_{on}}{\displaystyle PLP\cdot C^2\cdot(1-\rho)^2}
  \end{cases}
\end{equation}
\end{spacing}