Is the Federal Reserve Bank of the United States solvent?

Is the Fed solvent?

Read this (several times), quoted verbatim from John Mauldin:

"As a side note, it's probably worth noting that the Federal Reserve has already pushed its balance sheet to a point where it is leveraged 50-to-1 against its capital ($2.65 trillion / $52.6 billion in capital as reported the Fed's consolidated balance sheet ). This is a greater leverage ratio than Bear Stearns or Fannie Mae, with similar interest rate risk but less default risk. The Fed holds roughly $1.3 trillion in Treasury debt, $937 billion in mortgage securities by Fannie and Freddie, $132 billion of direct obligations of Fannie, Freddie and the FHLB, and nearly $80 billion in TIPS and T-bills. The maturity distribution of these assets works out to an average duration of about 6 years, which implies that the Fed would lose roughly 6% in value for every 100 basis points higher in long-term interest rates. Given that the Fed only holds 2% in capital against these assets, a 35-basis point increase in long-term yields would effectively wipe out the Fed's capital. "

How, under these circumstances, can the Fed ever tighten without massive sales of assets that would force the economy into a depression? Answer me that.