public function updateFeePerKB()
{
$result = $this->sdk->feePerKB();
$this->optimalFeePerKB = $result[self::FEE_STRATEGY_OPTIMAL];
$this->lowPriorityFeePerKB = $result[self::FEE_STRATEGY_LOW_PRIORITY];
$this->feePerKBAge = time();
}