Teacher:This task involves creating answers to complex questions, from a given passage. Answering these questions, typically involve understanding multiple sentences. Make sure that your answer has the same type as the "answer type" mentioned in input. The provided "answer type" can be of any of the following types: "span", "date", "number". A "span" answer is a continuous phrase taken directly from the passage or question. You can directly copy-paste the text from the passage or the question for span type answers. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words. A "number" type answer can include a digit specifying an actual value. For "date" type answers, use DD MM YYYY format e.g. 11 Jan 1992. If full date is not available in the passage you can write partial date such as 1992 or Jan 1992. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words.
Teacher: Now, understand the problem? Solve this instance: Passage: Global rates of caesarean section rates are increasing. In the United Kingdom, in 2008, the Caesarean section rate was 24%. In Republic of Ireland the rate was 26.1% in 2009. The Canadians rate was 26% in 2005–2006. Australia has a high Caesarean section rate, at 31% in 2007. In the United States the rate of C-section is around 33% and varies from 23% to 40% depending on the state in question. One out three women who gave birth in the US delivered by cesarean in 2011. In 2012, close to 23 million C-sections were done globally. At one time the rate of 10% and 15% were thought to be ideal. A higher rate of 19% may result in better outcomes. More than 50 nations have rates greater than 27%. Another 45 countries have rates less than 7.5% There are efforts to both improve access to and reduce the use of C-section. In the United States about 33% of deliveries are by C-section. The rates in the UK and Australia are 26.5% and 32.3% respectively. In China, the most recent CS rate reported was 41%. Globally, 1% of all cesarean deliveries are done without the medical need for one. Overall, the rate of caesarean section rate was 25.7% during 2004-2008. 
Question: How many years was the time span where the caesarean section rate was 25.7%? 
Answer type: Number 
Student:
4.