Answer: Yes. Marit's note is a demand note.
Explanation: basically, in finance, a demand note is "A note that normally has NO DATE for repayment, but is due on demand of the lender. Usually the lender will only give the borrower a few days notice before the payment is due."
In essence, a demand note, only has to state payable on demand.
If no time for payment is specified, then the payment is also payable on demand. Here, the note required installments but did not state a date for their payments.