(b)C lends money to B on the security of a joint and several promissory note made in C's favour by B, and by A as surety for B, together with a bill of sale of B's furniture, which gives power to C to sell the furniture, and apply the proceeds in discharge of the note. Subsequently, C sells the furniture, but, owing to his misconduct and wilful negligence, only a small price is realized. A is discharged from liability on the note.