The mathematics paper today seems pretty hard. Okay, few questions are quite easy, but the rest just pest me off. Even the first question tricked some of my friends, eventhough it's a very simple question. Fortunately, I remember very clearly that natural logarithm function (ln) cannot be integrated directly, but only by substitution method. I had a problem with one question, which I used up three pages to calculate but to no avail. Sigh.