Calculate the $99\%$ confidence interval for the difference $(1-2)$ of two population means given the following sampling results. Population $1$ : sample size $=12,$ sample mean $=16\mathrm{.}76,$ sample standard deviation $=1\mathrm{.}45.$ Population $2$: sample size $=7,$ sample mean $=15\mathrm{.}82,$ sample standard deviation $=0\mathrm{.}90.$

Your answer: