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ProModel records tank levels in a pre-defined array called Tank_Level where each element of the array corresponds to each tank location in the location list. For example, the level of TankA is the value of Tank_Level [TankA]. If TankA were the third location in the location list, you could also reference the level of TankA with Tank_Level[3]. For best results, you should control all tank levels using only the pre-defined tank filling and emptying subroutines rather than change the Tank_Level array values directly. This will prevent overfilling or overdrawing and will accurately gather statistics for each tank. For example, calling Tank_Fill (TankA, 500, 30, 0) automatically fills TankA to 500 units at a rate of 30 units per minute. The 0 signifies that the tank will not accept excess material and, as a result, an error message will occur if the tank reaches capacity before the specified amount fills into the tank.