Now, once again, just the process of writing it down and explaining it on this forum has helped me have a brainwave I think! I've been musing on this all day and it's just hit me... So here is my working:
take out the factors of t
Now here, I went to this:
But I think now, because
then for the integral is 0. So I should change the upper limit at this point to 3, and get:
Does that all seem good?!