scheme - スキーム内のデータ定義?

Question

私は今日これに取り組んできましたが、私がやらなければならないことは、アテンダントを取り、アテンダントが割り当てられている動物の合計年齢を返す関数を開発することです. たとえば、アテンダントのデイブを例にとると、10 になります。どこから始めればよいかわかりません。年齢を足すとどうなりますか？

(define-struct animal (name species age breakfasthour dinnerhour))
    (define-struct attendant (name a1 a2 a3))


    (define gorilla (make-animal "Koko" "Gorilla" "4" "8" "10"))
    (define bat (make-animal "Bruce" "Bat" "1" "23" "5"))
    (define mandrill (make-animal "Manny" "Mandrill" "5" "8" "7"))
    (define crocodile (make-animal "Swampy" "Crocodile" "1" "10" "8"))
    (define ocelot (make-animal "Ozzy" "Ocelot" "7" "7" "17"))
    (define capybara (make-animal "Capy" "Capybara" "4" "6" "8"))
    (define potto (make-animal "Spot" "Potto" "2" "2" "6"))
    (define tapir (make-animal "Stripey" "Tapir" "3" "10" "6"))
    (define vulture (make-animal "Beaky" "Vulture" "10" "9" "6"))


    (define attendant1 (make-attendant "Dave" gorilla bat mandrill))
    (define attendant2 (make-attendant "John" crocodile ocelot capybara))
    (define attendant3 (make-attendant "Joe" potto tapir vulture))


    #;(define (meal-time? e1 e2)
      (string=? (animal-species e1)
                (animal-dinnerhour e2)))



    #;(define (animal-template s...)
      (...(animal-name s)...
          (animal-species s)...
          (animal-age s)...
          (animal-breakfasthour s)...
          (animal-dinnerhour s)...))

    #;(define (attendant-template s...)
      (...(attendant-name s)...
          (attendant-s1 s)...
          (attendant-s2 s)...
          (attendant-s3 s)...))