i am wondering how a Miner chooses the transactions, he want to mine inside a block. For example, a Miner has got the Transactions T1 and T2 at the moment he starts a new mining work. This Miner is the one, finding the next block, which is after 10 seconds. After 8 seconds and 2 seconds before the Miner would find the next block T3 arrives at the Miner. Which transactions does the Miner then mine into the next Block, only T1 and T2 or also T3? (I assume here, the block size is bigger than the combined size of T1,T2 and T3.
So does the Miner determine at the beginning of a new mining process, which transactions go into the next block and ignores incoming transactions during the mining process of the next block?