Rental Income

I wanted to report my rental income on T776 . my tenant pay rent of $27600.00 annually and I pay bank mortgage of $24000.00 annually. What gross rent should I report ?  

a. Is it the $27600.00 rent paid by my tenant?

b. Or the different of $3600.00 of rent pay $27600.00  and mortgage $24000.00 ?

Thank you.