Two situations of Delta SA, which settles in shares with parties other than its employees. Situation A: a training body gives sessions each quarter, and public rates exist for comparable sessions. Situation B: an expert receives shares for specific research work, delivered over the year, with no market equivalent or comparison price, so that its fair value cannot be estimated reliably (case facts). Write an assessment note: is the presumption of reliable estimation rebutted in each situation, and what measurement basis follows?