function getRate() constant returns (uint8) {
    if      (block.timestamp < START)            return 166; 
    else if (block.timestamp <= START +  6 days) return 162; 
    else if (block.timestamp <= START + 13 days) return 156; 
    else if (block.timestamp <= START + 20 days) return 150; 
    else if (block.timestamp <= START + 27 days) return 144; 
    else if (block.timestamp <= START + 34 days) return 138; 
    else if (block.timestamp <= START + 41 days) return 132; 
    else if (block.timestamp <= START + 48 days) return 126; 
    return 120; 
  }