For every additional unit sold the profit increases v by $ 54 3. [-/2 Points] DETAILS HARMATHAP12 1. R.066. MY NOTES ASK YOUR TEACHER A retired couple have $900,000 to invest and want to earn $90,000 per year in interest. The safer investment yields 9.5%, but they can supplement their earnings by investing some of their money at 11%, How much should they invest at each rate to earn $90,000 per year? They should invest at 9.5% and at 11%. 4. [-/4 Points] DETAILS HARMATHAP12 1