Can we update attribute fields using Awards RestAPI

We would like to capture Award Close Date in a Flex DFF field - ATTRIBUTE_DATE9 on GMS_AWARD_HEADERS_B table. How can we update attribute DFF field using Awards using RestAPI?

End Point URL - /fscmRestApi/resources/11.13.18.05/awards/{AwardId}

Method - Patch

JSON file:

{

"AttributeDate9": "2023-12-31",

"CloseDate" : "2024-03-22"

}

Are Attribute fields exposed to the RESTAPI. If so, what should be the JSON code line for Flex fields?