Step 1: Read the chart and get the total age of each area in 2000:
Average ages on April 1 of 2000, 2001, 2002, 2003 are: Marketing 49.33, 44, 45, 46; OB 50.5, 51.5, 52.5, 47.8; Finance 50.2, 49, 45, 46; OM 45, 43, 44, 45.
Initial members: Marketing 3, OB 4, Finance 5, OM 6. So the total ages on April 1, 2000 are: Marketing \(3\times 49.33=148\), OB \(4\times 50.5=202\), Finance \(5\times 50.2=251\), OM \(6\times 45=270\).
Step 2: Track each area year by year:
Rule: with no joiner and no retiree, the total age rises by the number of members (everyone is one year older); a joiner adds 25 to the total, a retiree removes his/her age.
Marketing: 2001 average 44. With 4 members the total would be 176 = 148 + 3 + 25. So one person joined in 2001. Then 2002: \(4\times 45=180=176+4\) and 2003: \(4\times 46=184=180+4\). No retirement.
OB: 2001: \(4\times 51.5=206=202+4\), 2002: \(4\times 52.5=210=206+4\) (no change in members). 2003: \(5\times 47.8=239=210+4+25\), so one person joined in 2003. No retirement.
OM: 2001: \(7\times 43=301=270+6+25\), so one person joined in 2001. 2002: \(7\times 44=308=301+7\); 2003: \(7\times 45=315=308+7\). No retirement.
Finance: 2001 average 49. With no change the total would be \(251+5=256\) (average 51.2); with only a joiner it would be \((256+25)/6\approx 46.8\). Neither equals 49. With only a retirement the 4 remaining members have total \(256-60=196=4\times 49\), which matches: a member aged 60 on April 1, 2001 (59 a year earlier) retired from Finance.
Step 3: Check the Finance joiner:
2002: \(5\times 45=225=196+4+25\), so a new member joined Finance in 2002. 2003: \(5\times 46=230=225+5\). Everything is consistent, and the one retirement at age 60 is in Finance.
Final Answer:
The correct option is (3): Finance