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

In March 2013, the Blackstone Group and Carl Icahn expressed interest in purchasing Dell. In April 2013, Blackstone withdrew their offer, citing deteriorating business. Other private equity firms such as KKR & Co. and TPG Capital declined to submit alternative bids for Dell, citing the uncertain market for personal computers and competitive pressures, so the "wide-open bidding war" never materialized. Analysts said that the biggest challenge facing Silver Lake would be to find an “exit strategy” to profit from its investment, which would be when the company would hold an IPO to go public again, and one warned “But even if you can get a $25bn enterprise value for Dell, it will take years to get out.”

What year did the Blackstone Group express interest in selling Dell?
unanswerable