The flask of a rotary evaporator initially contains $10$ kg of grape juice. The rate of evaporation of water given as mv$=0\mathrm{.}09-0\mathrm{.}0004$t$,$where,mv in kg $/$ min and t is time in minutes. The concentration of juice in the flask was measured to be $35\backslash$deg Brix after $80$ minutes. Determine the initial concentration of grape juice in $\backslash$deg Brix.

a$)21,38$

b$)8,46$

c$)10\mathrm{.}35$

d$)12\mathrm{.}28$

e$)14\mathrm{.}28$