A door$-$to$-$door salesperson knocks on Kacey's door and convinces her to purchase the Wonder Vacuum for $$500.$ Soon after the salesperson leaves, Kacey begins to have second thoughts about the transaction. Which of the following statements about the situation is correct?

a$.$

Kacey must pay for the vacuum, but she can get a refund if she returns it to the manufacturer within $30$ days.

b$.$

Kacey can keep the vacuum without paying when it is delivered, as it was purchased in her home.

c$.$

Kacey can cancel the transaction at any time before midnight of the third business day thereafter.

d$.$

Kacey agreed to purchase the vacuum, so she must honor the agreement.