This is a great question! You could be held responsible for the consequences, but that does not necessarily mean you would be "called to account" for them. Where as if you are accountable for the consequences it is assumed you were responsible and are the one who suffers the consequences of the situation. Such as "A young child may break someones window, but his parents will be held accountable." They are often used interchangeably and this situation totes the grey line. In this situation I would choose accountable. I hope that helps a little :)

It is your responsibility (you are in charge) to make sure you can get the money back to him in time. If you do not return the money to him within 10 days then you will be held accountable (you must fix the problem) for it as you borrowed it, not anyone else. More examples: You are responsible for practicing your English and getting better If you break a window, you will be held accountable and will have to fix it. Hope this helps! Vicki