\begin{axis}[%
  width  = 80mm
 ,height = 50mm
 ,xlabel = {Time}
 ,ylabel = {Production}
 ,xmin   = 0
 ,xmax   = 5
 ,legend entries = {Quadratic, Logarithmic}
 ,legend style   = {legend pos = north west}
]

\addplot[red] {x^2};
\addplot[blue] {x*log2(x)};

\end{axis}