Well, then all it's lost, ain't it...or not? What do you mean you don't have more tries for the assignment? Is this an online hw and you have to type in the answers in some site? That is, imo, lame, but if that's what you've to do and you only have few trials, why don't you first check thoroughly the deveopment of the problem and the answer?!
You've been given the complete answer, now you have to plug in upper and lower limits, be careful and dp some fractions algebra and a little rules of logarithsm and that's all there is to it.
Tonio