如图，$\mathit{AB}//\mathit{CD}$，点$E$是$\mathit{CD}$上一点，$\angle \mathit{AEC}=42°$，$\mathit{EF}$平分$\angle \mathit{AED}$交$\mathit{AB}$于点$F$，求$\angle \mathit{AFE}$的度数．