a) Given that the decimal representation of $5^{2018}$ has 1411 digits and starts with 3 (the leftmost non-zero digit is 3), for how many integers $1 \leq n \leq 2017$ does the number $5^{n}$ start with 1?

b) The integers $4^{52}$ and $5^{52}$ both start with the digit 2. If the decimal representations of the powers $4^{n}$ and $5^{n}$, with $n>0$ and integer, start with the same digit $d$, what are the possible values of this digit?