Select the correct statement(s):

Where $\mathrm{a}, \mathrm{b}, \mathrm{c}, \mathrm{d}, \mathrm{e}, \mathrm{f}, \mathrm{g}, \mathrm{h}$ are $3^{\mathrm{rd}}$ period elements. If the difference between the atomic numbers of elements $\mathrm{b}$ and $\mathrm{e}$ is $\mathrm{x}$ and the difference between the atomic number of elements $\mathrm{c}$ and $\mathrm{f}$ is $\mathrm{y}.$ What is the value of $\mathrm{x}-\mathrm{y}.$