The University of SydneyPage 18Constructing a block–Transactions are selected from the memory pool.–Transactions are prioritized to include old and high-value transactions into the current block–Priority = sum (value of inputs * input age)/ Transaction size–First 50KB of transaction space on a block is set aside for high-priority transactions.–Note: transaction fee is not considered.–Rest is filled up to the maximum block size by minimum fee transactions and then if there is space no-fee transactions are included.–Miners may ignore to include transactions without fees–Transactions left in the memory pool will remain there to be included in the next block.