First or third class mailers?

Suppose you're trying to optimize a mailing campaign where physical mail is sent to potential customers. There are two options to send advertising mail, either first class or third class. First-class costs $0.50 per parcel with a delivery rate of 99% and third-class costs $0.35 per parcel with a delivery rate of 65%. Third-class mail also receives a volume discount, if a batch of parcels is greater than 500, for first 500 are $0.35 and anything additional costs $0.32 per parcel.

Questions:

• Which option is the best for the company?
• Assume our goal is to reach as many people with a cap of $1000, which option would be the best?
• Assume our goal is to reach 100 people, what option is best?