Central excise-whether quantity discount given to related pe

Please help.

Problem is that 'A' co. is procurring r.m. selling and also allowing to use their brand name for which they are receiving royalty to 'B' . 'B' company manufactures finished goods with packing & brand name of 'A' and selling 90% to 'C' company after deducting 50% quantity discount. 'C' company is related company of 'A'. in this situation whether quantity discount claimed by 'B' is admissible for the purpose of calculation of central excise duty?

thanks, in advance.