Starting with RemoteFunctions and not sure what I am doing wrong. Help!?

game.ReplicatedStorage.RemoteFunction.OnServerInvoke(player,a,b,c) 	if a == "tron" then 		if b == "on" then 			workspace.Titantrons[c].Main.Launch:Play() 		end 	end 	return a,b,c; end

I'm not sure what I'm doing wrong but there's an error line under the end.