Answer:
It would be wiser for the couple to stay in the old apartment and save $1400
Explanation:
If they stay until the end of the lease, total money that will be paid out is $1000 x 6 = $6000,
If they leave, they'll have to forgo $1000.
If they move to their new apartment, they'll pay $900 x 6 = $5400
total expenditure if they move to the new place at the end of the six months period will be, the $1000 that will not be refunded back to them on the old apartment, plus this new $5600 for six month's rent in this new apartment, and that will be a total of $6400.
It would be wiser for the couple to stay in the old apartment and save $1400