Passage: The link replaced a ferry service, which had been the primary means of crossing the Great Belt. After more than 50 years of debate, the decision to construct a link was made in 1986; it opened to rail traffic in 1997 and to road traffic in 1998. At an estimated cost of DKK 21.4 billion (1988 prices), the link is the largest construction project in Danish history. It has reduced travel times significantly; previously taking one hour by ferry, the Great Belt can now be crossed in ten minutes. This link and the Øresund Bridge (built 1995–1999) have together enabled driving from mainland Europe to Sweden and the rest of Scandinavia through Denmark.

Question: What was the estimated price for the construction project?
DKK 21.4 billion (1988 prices)