code: public void assignAmount(XAttribute attribute, Double amount) {
  		if (amount != null && amount > 0.0) {
  			XAttributeContinuous attr = (XAttributeContinuous) ATTR_AMOUNT
  					.clone();
  			attr.setValue(amount);
  			attribute.getAttributes().put(KEY_AMOUNT, attr);
  		}
  	}
docs: Assigns any attribute its cost amount, as defined by this extension's
  amount attribute.
  
  @param attribute
  Attribute to assign cost amount to.
  @param amount
  The cost amount to be assigned.