int rate futures

Of course they do! But in most answers it is done indirectly because most of the answers use ticks. I explain in the lectures that the value of 1 tick is the contract size x 0.01 / 400, and so the dividing by 400 is taken into account there. You are welcome to use ticks in the exam, but I think it is easier to do it the way in the lectures - it gives always exactly the same answer.