dear sir

A LNG ship can be propelled on
1) Heavy fuel oil or
2) it can be using nBOG + heavy fuel oil or
3) it can be steam turbine propelled or
4) it could be using the nBOG and forced BOG for main propulsion.

How do i calculate the bunker cost ? With only FO, given sfc and power it can be calculated. But in dual mode how to calculate ? In an steam turbine propelled ships hwo t calculate the fuel consumption.

For number 2, 3, 4 how to calculate the bunker consumption ?