Held that the assessee has maintained separate books of account for each unit, eligible for deduction under S. 10AA, 80-IC and 80-IE and the in-house R&D expenditure was incurred at a centralised R&D facility; the disallowance made by the AO by allocating a portion of common research and development expenses to the said tax-exempt units is not sustainable. (AY. 2015-16)