Refer to figures.
Basic Empty Mass (BEM) is the mass of the helicopter and all its basic equipment and that of the declared quantity of unusable fuel. It also includes any fixed ballas, full operating fluids.

Take-Off Mass (TOM) is the mass of a helicopter including everything and everyone contained within it at the start of the take-off run. Therefore, a simple calculation of adding all the information together is needed.

Dry Operating Mass (DOM) is the total mass of the helicopter ready for a specific type of operation excluding all usable fuel and traffic load. The dry operating mass includes the items below, known as Variable Load (VL):

• Crew and crew baggage
• Catering and removable passenger service equipment
• Portable water and lavatory chemicals
• Food and beverages.

Traffic load (TL) in a helicopter refers to the number of passengers or cargo that the aircraft is carrying at a given time. It is used to determine the weight and balance of the helicopter, which is important for safe flight. The maximum traffic load of a helicopter is determined by its design and is specified in its flight manual.

Zero Fuel Mass (ZFM) is the term used to describe the DOM plus TL but excluding fuel.

Useful Load (UL) consists of the fuel onboard for a flight and traffic load.

NOTE:
For this type of questions, it’s advised to make a table with the different masses. Thus, giving a visual and simplified way of solving the question.