Benson Bank's startup division establishes new branch banks. Each branch opens with three tellers. Total teller cost per branch is $$93,000$ per year. The three tellers combined can process up to $85,000$ customer transactions per year. If a branch does not attain a volume of at least $55,000$ transactions during its first year of operations, it is closed. If the demand for services exceeds $85,000$ transactions, an additional teller is hired and the branch is transferred from the startup division to regular operations. Determine the amount of teller cost in total and the average teller cost per branch for Benson Bank, assuming that the startup division operates $20,25,30$ or $35$ branches. In this case $($the activity base is the number of branches$),$ is the teller cost a fixed or a variable cost?