acid base - Finding pH after dilution?

Assume that $\ce{pKa}$ is 4.76

Mix $\pu{50 mL}$ of $\pu{0.1M}$ $\ce{HA}$ and $\pu{50 mL}$ $\pu{0.1M}$ $\ce{NaA}$. This is solution (i). Calculate concentrations of $\ce{HA}$ and $\ce{A-}$, measure the $\ce{pH}$.

Then, mix $\ce{10 mL}$ of solution (i) and $\ce{90 mL}$ of water. Calculate $\ce{[HA]}$ and $\ce{[A-]}$, and measure the $\ce{pH}$.

How do I approach these calculations? I have 13 of these to do, these are the first two.

Equation is:

$$\ce{pH} = \ce{pKa}+\log{\left(\frac{\ce{[A-]}} {\ce{[HA]}}\right)}$$

For the first one, I got,

$$4.76 + \log{\left(\frac{0.1}{0.1}\right) = 4.76}$$ But I don't know if that's correct. How would I approach the subsequent problem when water is added?