(Ch.23) Portfolio returns, in %, over the first six months of a year were 0.16, 0.78, 0.39, 0.56, 1.18, and -0.13. The benchmark returns over the same six months were 0.33, 0.59, -0.81, 0.43, 1.63, and 0.03, respectively. What is the portfolio's monthly (i.e., NOT annualized) tracking error over the period? (Round to the nearest 0.01%, drop the % symbol; e.g., if your answer is 0.135%, record it as 0.14.)