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: Carboplatin was given at a fixed target area under the concentration - time curve of 6 . 0 by the Calvert formula , whereas paclitaxel was escalated in patient cohorts from 150 mg / m2 ( dose level I ) to 175 , 200 , 225 , and 250 mg / m2 .
### Output Text:
<span class="chemical">Carboplatin</span> was given at a fixed target area under the concentration - time curve of 6 . 0 by the Calvert formula , whereas <span class="chemical">paclitaxel</span> was escalated in patient cohorts from 150 mg / m2 ( dose level I ) to 175 , 200 , 225 , and 250 mg / m2 . 