uint256 constant BLOCK_PERIOD = 13 seconds;
uint256 constant PRIORITY_EXPIRATION_PERIOD = 3 days;
/// @dev Expiration delta for priority request to be satisfied (in ETH blocks)
uint256 constant PRIORITY_EXPIRATION = PRIORITY_EXPIRATION_PERIOD/BLOCK_PERIOD;
>>> 3*24*60*60 / 13    # 3 days / 13 sec block period
19938.46153846154
>>> 3*24*60*60 / 12    # 3 days / 12 sec block period
21600.0
>>> 21600 - 19938      # difference in blocks
1662
>>> 1662 * 12 / (60 * 60) # difference in hours
5.54
uint256 constant BLOCK_PERIOD = 12 seconds;
