After graduating from dental school two years ago, Dr$.$ Lisa Anderson purchased the dental

practice of a long$-$time dentist who was retiring. In January of this year, she had to replace

the outdated autoclave equipment she inherited from the previous dentist. Now, as she is

preparing her budget for next year, she is concerned about understanding how her cost for

sterilizing her dental instruments has changed. She has gathered the following information

from her records: