You are considering to use natural gas commodity to diversify your stock portfolio. You find that the long run variance of your portfolio and natural gas is $12\%,45\%($annualized$),$ and the long$-$run corresponding covariance is $-18\%.$ If today$$s return of your portfolio and natural gas is $0\mathrm{.}3\%$ and $0\mathrm{.}7\%,$ please find the correlation between your portfolio and natural gas by using the RiskMetrics model.