In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: After admission , the patient received a continuous intravenous infusion of 5 - FU ( 1000 mg / day ) , during which precordial pain with right bundle branch block occurred concomitantly with a high serum FBAL concentration of 1955 ng / ml .
### Output Text:
After admission , the patient received a continuous intravenous infusion of <span class="chemical">5 - FU</span> ( 1000 mg / day ) , during which precordial pain with right bundle branch block occurred concomitantly with a high serum <span class="chemical">FBAL</span> concentration of 1955 ng / ml . 