8) A novel Penelope has woven a web throughout 1999, from the first to the last day. Every morning she wove $20 \mathrm{~cm}$ of web and every afternoon she undid some, precisely $20 \mathrm{~cm}$ on even days of the month and $19 \mathrm{~cm}$ on odd days. How long was the web at the end?
(A) $140 \mathrm{~cm}$
(B) $172 \mathrm{~cm}$
(C) $186 \mathrm{~cm}$
(D) $200 \mathrm{~cm}$
(E) $210 \mathrm{~cm}$.
8) The answer is (C)

Every evening of an odd day of the month, the web grew by $1 \mathrm{~cm}$, while its length remained unchanged on the evening of every even day. The odd days of the year 1999 were 16 for each of the 7 months with 31 days, 15 for each of the 4 months with 30 days, and 14 in the month of February. The length of the web at the end of the year was therefore $16 \times 7 + 15 \times 4 + 14 = 186 \mathrm{~cm}$.