Why must old currency be taken out of circulation when new currency is made?

Used cars usually have options: higher depreciation rate than new cars lower financing costs than new cars lower insurance premiums than new cars lower maintenance costs than new cars

Specialization—the division of labor—enhances productivity and efficiency by a) allowing workers to take advantage of existing differences in their abilities and skills. b) avoiding the time loss involved in shifting from one production task to another. c) allowing workers to develop skills by working on one, or a limited number, of tasks. d)all of the means identified in the other answers.

On january 1, 2017, sophie's sunlounge owned 4 tanning beds valued at $20,000. during 2017, sophie's bought 3 new beds at a total cost of $14 comma 000, and at the end of the year the market value of all of sophie's beds was $24 comma 000. what was sophie's net investment