If f is differentiable on an open interval, then f is said to be concave down on the open interval if a. f1 is undefined on that interval. b. f1 is constant on that interval. c. f1 is increasing on that interval. d. f1 is decreasing on that interval.

Paula makes stained-glass windows and sells them to boutique stores. if her costs total $12,000 per year plus $4 per window for the frame. how many windows must she produce to earn a profit of at least $48,000 in one year if she sells the windows for $28 each? 1. define a variable for the situation. 2. write an inequality that represents her profit. note: revenue is money coming in. cost is money going out. profit is the difference between the revenue and the cost. in other words: revenue - costs profit 3.using words, describe how many windows she must sell to have a profit of at least $48,000.