Answer:
Yes, they should claim the foreign tax credit.
Explanation:
'Martha and Lew' are taxpayers and are married. If they claim the credit, then they will get the tax benefit on the whole amount of $400. In case they get the deduction done for foreign taxes they will have a $100 tax benefit (given tax rate % is 25% on $400).
It is generally better to claim the credit for qualified foreign taxes in comparison to getting them deducted as an itemized deduction. If one chooses to take the 'foreign tax credit', and the taxes that have been paid exceed the credit limit for the tax year, then the excess can be carried over to the next year.
Thus, Martha and Lew should claim the foreign tax credit.