Capital gains/depreciation

Mr. A has 2 proprietary business units (X & Y). During the year 1 business unit ‘X’ has sold its entire plant & machinery (only assets in fixed assets group) thereby incurring a short term loss of ` 2,51,911/- Now my query is, Since the entire block of asset cease to exist in Business Unit ‘X’: 1. whether the short term loss of ` 2.52 Lacs will be allowed to be carried forward as Short term Loss u/s 71, or 2. Whether it will be adjusted against Plant & Machinery block of assets of Business Unit ‘Y’. In case of Option No. 1 how the same will be reflected in ITR-4. Kindly Help….