Okay, here we have this:
We are going to find first the diagonal of the square, and the y-coordinate will be the diagonal divided by 2, and we can see that the x-coordinate is equal to 0.
To find the length of the diagonal we will use the Pythagorean theorem:
[tex]\begin{gathered} c^2=a^2+b^2 \\ c=\sqrt[]{7^2+7^2} \\ c=\sqrt[]{49+49} \\ c=\sqrt[]{98} \\ c=\sqrt[]{2}\sqrt[]{7}^2 \\ c=7\sqrt[]{2} \end{gathered}[/tex]And as the y-coordinate is half the length of the diagonal we get that it is:
y=c/2
y=(7√2)/2
Finally we obtain that the coordinate of Q is: (0,7/2√2). The correct option is the option B.