abnormal gain

Have you watched my free lectures working through this example? The abnormal gains are valued at the full cost per unit. The amount of gain that would appear in the profit statement is the value of the gains less any scrap value (because we would not be receiving the scrap value that would have been expected had there not been the gain).

Yes I have watched the related lecture, and still have some questions about how the loss account is established.

Well do ask whatever question you have (although appreciate that you obviously cannot be asked to write up a loss account in the exam).