The analysis of three different binary oxides of bromine (Br) and...

The analysis of three different binary oxides of bromine $(\mathrm{Br})$ and oxygen $(\mathrm{O})$ gives the following results:

Compound	Mass of O combined with 1.0 g of Br
$\mathbf{X}$	0.101 g
$\mathbf{Y}$	0.303 g
$\mathbf{Z}$	0.503 g

Which of the following statements is not correct? I Compound $\mathbf{Y}$ is $\mathrm{Br}_2 \mathrm{O}_3$ II Compound $\mathbf{Z}$ is $\mathrm{Br}_2 \mathrm{O}_5$ III Compound $\mathbf{Z}$ is $\mathrm{Br}_2 \mathrm{O}_7$ IV Compound $\mathbf{Y}$ is $\mathrm{Br}_2 \mathrm{O}_5$