A simultaneous increase in both the demand for MP3 players and the supply of MP3 players would imply that
a. both the value of MP3 players to consumers and the cost of producing MP3 players has
increased.
b. both the value of MP3 players to consumers and the cost of producing MP3 players has
decreased.
c. the value of MP3 players to consumers has decreased, and the cost of producing MP3
players has increased.
d. the value of MP3 players to consumers has increased, and the cost of producing MP3
players has decreased.