The redeem function converts a specified quantity of aTokens into the underlying asset, and returns them to the user. The amount of underlying tokens received is equal to the quantity of aTokens redeemed, multiplied by the current Exchange Rate. The amount redeemed must be less than the user's Account Liquidity and the market's available liquidity.
AErc20 / CEther
function redeem(uint redeemTokens) returns (uint)
msg.sender: The account to which redeemed funds shall be transferred.
redeemTokens: The number of aTokens to be redeemed.