Guess the Trade
Sam and Alex are portfolio managers and they've recently joined a crypto trading platform where Caroline is a top-performing trader. Caroline mentions she recently made a significant profit from trading a particular cryptocurrency in some specific amount, but won't directly reveal the details. Instead, she gives them a list of 10 possible combinations of cryptocurrencies and quantities:

Bitcoin: 15 coins, 16 coins, 19 coins.
Ethereum: 17 coins, 18 coins.
Cardano: 14 coins, 16 coins.
Solana: 14 coins, 15 coins, 17 coins.

Caroline then privately tells Sam the type of cryptocurrency and Alex the quantity she traded. The following conversation takes place:

Sam (to Alex): I don't know which was the profitable trade, but I'm sure you don't know either.
Alex: At first I wasn't sure which trade was profitable, but now I do.
Sam: In that case, I also know which cryptocurrency and in what quantity Caroline traded profitably.

From this conversation, which cryptocurrency and in what quantity did Caroline make the profitable trade?