afb systems is considering a new marketing campaign that will require the addition of a new computer programmer and new software. the programmer will occupy an office in afb's current building and will be paid $8,000 per month. the software license costs $1,000 per month. the rent for the building is $4,000 per month. afb's computer system is always on, so running the new software will not change the current monthly electric bill of $900. the incremental expenses for the new marketing campaign are group of answer choices $13,900 per month $13,000 per month $8,000 per month $9,000 per month