How do I refer the docker image tag using the variable in the below Concourse YAML file ? The below YAML file is giving me the error "failed to interpolate task config: undefined vars: DOCKERBOX_VERSION"

jobs:
- name: build
  plan:
  - task: run-script
    config:
      platform: linux
      image_resource:
        type: docker-image
        source:
          repository: hubpany/group/concourse/dockerbox
          tag: ((DOCKERBOX_VERSION))
      params:
        DOCKERBOX_VERSION: 3.0.0
      run:
        path: sh
        args:
          - -exc
          - |
            echo "DOCKERBOX_VERSION is set to: $DOCKERBOX_VERSION"
            # Add your script commands here
            echo "Script completed."