How is a deduction for any potential excess investment interest treated? Why is it treated this way?

1. Robin's financial records from 2020 show the following information from the forms she received: Interest income from bank CD's: $1,600 Taxable annuity payment total: $3,200 City ad valorem property on investments: $240 Investment interest expense: $5.600 Calculate Robin's net investment income and her current investment deduction. How is a deduction for any potential excess investment interest treated? Why is it treated this way