Read this and answer the question. If the question is unanswerable, say "unanswerable".

In June 2009 the first major building work at the abbey for 250 years was proposed. A corona—a crown-like architectural feature—was intended to be built around the lantern over the central crossing, replacing an existing pyramidal structure dating from the 1950s. This was part of a wider £23m development of the abbey expected to be completed in 2013. On 4 August 2010 the Dean and Chapter announced that, "[a]fter a considerable amount of preliminary and exploratory work", efforts toward the construction of a corona would not be continued. In 2012, architects Panter Hudspith completed refurbishment of the 14th-century food-store originally used by the abbey's monks, converting it into a restaurant with English Oak furniture by Covent Garden-based furniture makers Luke Hughes and Company.

On what date did the Dean and Chapter announce that work would not be continued?
4 August 2010