Supply question

[*Lava*]

Hey!

When you are doing an amphibious assault, and you have the option to give supply to the ground unit from your ships (the ship icon to the right of the oiler replenishment icon), what exactly is being spent and how do you figure how much it actually costs?

Thanks for any help.

[AlvaroSousa]

it gives them 1 unit supply level and +6% effectiveness.
it doesn't cost you anything except operation points.

[*Lava*]

Thanks very much!