Help on batch render and mel command, urgent!

hi, folks,

i want to use following bat comamand to render my mb file, but now i need to add commmands to render layers, can you tell me what i have to add into the command lines. thanks a lot.

render -cam c1 -s 1 -e 120 -b 1 -of tga -rl on sky -rs on scenes_2_f.mb;

It should use the settings you set in the render globals unless the one son the comman line override which in thsi case do not.