a) 10,22 = 12*(1-e^{k*0,1})
10,22/12 = 1-e^{0,1*k}
e^{0,1*k} = 1-10,22/12
0,1*k = Ln (1-10,22/12)
k = Ln (1 - 10,22/12)/0,1
k = -19,083
b) U (0,2) = 12 * (1-e^{-19,083*0,2}) = 11,74
c) 6 = 12 * (1 - e^{-19,083*t})
e^{-19,083*t} = 0,5
-19,083 * t = Ln (0,5)
t = Ln (0,5) / -19,083 = 0,036