Incidentally, I don't know if you've enrolled in the KDP Select thing where you get promo days for free? My advice is - don't bother with the free days. The vast majority of the free sales are never even downloaded, let alone read - there's a huge amount of people who click on everything that's free for a given day. I read one guy boasting that he now had a quarter of a million books on his Amazon account, all free purchases, almost all of them never read.
It doesn't lead to increased exposure, reviews or sales - mostly because the sales for free books don't count for proper rankings, so as soon as the free day is over your book vanishes into the 200,000+ rank, so there's no momentum from it.
The one thing it is useful for is driving sequels - if you write a second book then put the first one up for free, it can drive sales for the second one. But for a single book, it ultimately does nothing.