= Solution
\b[The assignments are $\mathrm H_a$: $6.787$ ppm, $1$H, doublet of quartets; $\mathrm H_b$: $6.496$ ppm, $1$H, doublet of quartets; $\mathrm H_c$: $4.281$ ppm, $2$H, quartet; $\mathrm H_d$: $1.331$ ppm, $3$H, triplet.] The <chemical shift> of a multiplet is its centre, rather than its most downfield line.
Each vinylic <proton> has <scalar spin-spin coupling> to the other vinylic <proton> and to three equivalent spin-$\tfrac12$ <fluorine> nuclei. The first interaction produces a doublet, and the second a $1:3:3:1$ quartet: eight lines overall, partly interleaved for $\mathrm H_a$. The two <chemical shifts> differ because the vinylic sites have different substituents.
The ethoxy $\mathrm{OCH_2}$ <protons> are deshielded by <oxygen> and split into a $1:3:3:1$ quartet by the three methyl <protons>. The methyl <protons> are split into a $1:2:1$ triplet by the two equivalent methylene <protons>. The relative <NMR signal integrals> are $1:1:2:3$.
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