RDP 9601: Why Does the Australian Dollar Move so Closely with the Terms of Trade? Equation (C4)

\begin{matrix} \hat{a} = 1.06, & \hat{b} = - 0.00061, & {\hat{c}}_{1} = 0.90, & {\hat{c}}_{2} = 0.14, & {\hat{c}}_{3} = - 0.06, & {\hat{c}}_{4} = 0.12, & {\hat{c}}_{5} = - 0.33, & {\hat{σ}}_{ε_{1}} = 0.02 \end{matrix}