A) $ 60{}^\circ $
B) $ 45{}^\circ $
C) $ 36{}^\circ $
D) $ 80{}^\circ $
Correct Answer: A
$ \therefore $ $ \angle DOC=\frac{2}{3}\angle COA $ and $ \angle COE=\frac{3}{4},\angle BOC $
$ \Rightarrow $ $ \angle DOC=\frac{2}{3}\times 36{}^\circ =24{}^\circ $ and $ \angle COE=\frac{1}{4}(180{}^\circ -36{}^\circ )=\frac{1}{4}\times 144{}^\circ =36{}^\circ $
$ \therefore $ $ \angle DOE=\angle DOC+\angle COE=24{}^\circ +36{}^\circ =60{}^\circ $