When Ethyl Acetoacetate Is Treated with One Equivalent of Ethoxide $\delta$

Essay

When ethyl acetoacetate is treated with one equivalent of ethoxide ion followed by one equivalent of 1,2-dibromoethane compound,X is produced.Treatment of X with a second equivalent of ethoxide,produces Y.Further treatment of this product to conditions of saponification,acidification and heating produced a product,Z,that gives the following spectral data:
¹H NMR: 0.88 $\delta$ multiplet ¹³C NMR: Broad Band Decoupled: 10.40,21.17,29.84,
208.30 $\delta$
1.00 $\delta$ multiplet DEPT 90: 21.17 $\delta$
1.96 $\delta$ multiplet DEPT 135: positive signals at 21.17,29.84 $\delta$
2.24 $\delta$ singlet negative signals at 10.40 $\delta$
What is a reasonable structure for Z?