Answer:
As the bank manager, Steve should be informed that the promissory note met all conditions and the case cannot be seen in the same light as a fraud case because the bank had no reasons to suspect any kind of fraudulent activity as everything was filled correctly and no sign of tampering on the note, it was a genuine and verified promissory note. Aside from the amount and signature, there was nothing in the note to show the agreement that both Steve and Henry had, which is not going above $5,000.
So the bank has the right to collect all its money from Steve, it is a form of negligence on the part of Steve to leave the amount blank which Henry took advantage of.
Although Steve could sue Henry for going above the amount they both agreed on.