S .37(1) : Business expenditure-Short fall in inventory written off-Allowable as deduction-Purchase of tools allowable as revenue expenditure-Provision for warranty-Allowable as deduction-Lability for erection and commissioning placed upon shoulders of assessee-Provision at rate of one per cent. to three per cent. determined on basis of past experience-Matter remanded to the Assessing Officer. [S. 28(1)]