$1.$ In a single$-$effect evaporator, if the initial feed is $1000$ kg$/$hr with a concentration of $10\%$ solute and the final product is concentrated to $30\%$ solute, what is the mass of the evaporated water?

$-$ a$)500$ kg$/$hr

$-$ b$)667$ kg$/$hr

$-$ c$)700$ kg$/$hr

$-$ d$)750$ kg$/$hr