[From Mooney]. Assume that an IR system returns a ranked list of 10 total documents
for a given query. Assume that according to a gold-standard labelling
there are 6 relevant documents for this query, and that the only
relevant documents in the ranked list are in the 1st, 2nd, 5th, and
9th positions in the ranked results. Show the precision/recall curve
for this individual query.