A is renting an apartment for two years with the agreement to pay the monthly rentals on the first day of the month. Since Valentine's day is approaching, he asked his landlady named B to defer the payment for the month of January and February because he wanted to save the money to surprise his girlfriend. On March 1, A paid P500 as his monthly rental. B issued a receipt without specifying the month intended for the payment. What would be the presumption? Can B still collect the rentals for January and February? If yes, what will she do?

Answer based on legal reasoning or based on law.