成會固定成本和變動成本 - 會計

A student association has hired a band and a caterer for a graduation party.
The band will charge a fixed fee of $1,000 for an evening of music,and the
caterer will charge a fixed fee of $600 for the party setup and an additional
$9 per person.Students attending the party will pay $5 each at the door.


Compute the fixed cost,the variable cost,and total cost to the student
association.

假設有X位學生參加:
fixed cost:$1,000+600=$1,600
variable cost:$(9-5)x
^^^^^^^
請問為甚麼要扣掉$5呢?
$5不是收入嗎??
付給caterer的$9是成本嗎?既然是成本又為何又要扣掉收入$5呢?



想很久一直想不通><
請大大解答，謝謝:)))


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