a slight problem need some help. Simulation Control System

["Mr.Spark" <malmanea@gmail.com>]

I had a problem when I run examiner to check if the body package is
working fine but the problem it gives me:

Specification Part:

with Sensor, Pump;

--# inherit Sensor, Pump;

package Tank

--# own Tank_Level;
--# initializes Tank_Level;

is
   procedure Control;

   --# global out Tank_Level;
   --#        in Sensor.Level;
   --#        in out Pump.Pump_Open;
   --# derives Tank_Level from Sensor.Level &
   --#         Pump.Pump_Open from Sensor.Level, Pump.Pump_Open;


end Tank;

Body Package Is :

with Sensor, Pump;

package body Tank

is

   Empty: constant Sensor.Level_Type := 10;
   Full: constant Sensor.Level_Type := 60;

   -- this procedure controls the operation of pumps when they should
be opened
   -- or closed for the safety of the system. The pump will be closed
if the
   -- Water Level Tank is <= 10 and it will be Opened if the Water
Level
   -- in Tank >= 60.

   procedure Control
   is
      Tank_Level: Sensor.Level_Type;
   begin

      Tank_Level:= Sensor.Get_Level;
      if Tank_Level <= Empty then
         Pump.Close;
      elsif Tank_Level >= Full then
         Pump.Open;
      end if;
   end Control;

end Tank;


The errors that it shows are :


1.Semantic Error : Ilegal redeclaration of identifier Tank_Level;
2.Semantic Error : The Identifier is either undeclared or not visible
at his point
3.Semantic Error : The Identifier is either undeclared or not visible
at his point1.
4.Semantic Error : The Identifier is either undeclared or not visible
at his point
5.Semantic Error : The own variable Tank_Level does not have a
definition

If you could give me a hint how to solve this problem it would be
great.