Financial crisis of 2007%E2%80%9308:

During April 2009, U.S. Federal Reserve vice-chair Janet Yellen discussed these paradoxes: "Once this massive credit crunch hit, it didn’t take long before we were in a recession. The recession, in turn, deepened the credit crunch as demand and employment fell, and credit losses of financial institutions surged. Indeed, we have been in the grips of precisely this adverse feedback loop for more than a year. A process of balance sheet deleveraging has spread to nearly every corner of the economy. Consumers are pulling back on purchases, especially on durable goods, to build their savings. Businesses are cancelling planned investments and laying off workers to preserve cash. And, financial institutions are shrinking assets to bolster capital and improve their chances of weathering the current storm. Once again, Minsky understood this dynamic. He spoke of the paradox of deleveraging, in which precautions that may be smart for individuals and firms—and indeed essential to return the economy to a normal state—nevertheless magnify the distress of the economy as a whole."

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Who was the U.S. Federal Reserve vice-chair in April 2009?
Janet Yellen