Traffic Load (TL). The total mass of passengers, baggage and cargo, including any ’non-revenue’ load.

Dry Operating Mass (DOM). The total mass of the aeroplane ready for a specific type of operation excluding usable fuel and traffic load. The mass includes items such as crew and crew baggage, catering and removable passenger service equipment, potable water and lavatory chemicals, food and beverages.

Operating Mass (OM). The DOM plus fuel, but without traffic load.

OM = DOM + fuel = 2890 kg + 970 kg = 3860 kg

For this question, we will consider the take-off situation, subtracting from the Maximum Permissible Take-off Mass and the Performance Limited Landing Mass limits the OM, the TL and the fuel masses (as required), to figure out if the aircraft is overloaded or underloaded:

• Underload/Overload = Allowed take-off mass - Operating Mass (OM) - Traffic Load (TL)
  positive result (+) → underload
  negative result (-) → overload

Max TOM - OM - TL = 5450 - 3860 - 1420 = 170 kg underload

Note: Be careful to avoid any double mass calculations, due to the fact that some masses are already included in other masses, e.g. fuel mass is included in OM, crew and crew baggage mass is included in DOM, DOM is included in OM and so on.