A skim$-$milk stream with a flow$-$rate of $500$ kg$/$hour containing $93\%$ water, $6\%$ Protein,$0\mathrm{.}5\%$ ash and $0\mathrm{.}5\%$ fat is mixed with a stream with a flow$-$rate of $45$ kg$/$hour containing$35\%$ water, $62\%$ fat, $3\%$ protein. Determine the composition and flow$-$rate of the productstream.