Logarithm — NDA Mathematics PYQs

If $(10+{\log }_{10}x)$, $(10+{\log }_{10}y)$ and $(10+{\log }_{10}z)$ are in AP, then consider the following statements :
I. The GM of $x$ and $z$ is $y^2$.
II. The AM of ${\log }_{10}x$ and ${\log }_{10}z$ is ${\log }_{10}y$.
Which of the statements given above is/are correct?

Consider the following for the two (02) items that follow :
Let $p=\sum _{j=1}^n{\log }_{10}{2}^j$ and $q=\sum _{j=1}^n{\log }_{10}{5}^j$.

If $p+q=15$, then what is $q-p$ equal to?