For my friend's situation, this is probably a math question.
I don't have an answer.
But now he pays more interest than "capital", in other words, monthly
payment paid now covers interest primarily.
So maybe it is better to pay 100k now than in March????
Because if he pays 100k in March, he pays mortgage interests for December
January February based on 390,000.
If he pays now, he loses $500, but he saves the interest money in January
February.
Am I right? Sorry cannot type Chinese now.