You are examining the market for Tesla electric cars and observe that over time, more Teslas are purchased for a higher price than in the past. Which of the following events could cause this outcome?
a. A report is released claiming that new Teslas have security issue, making them easy to steal.
b. The cost of batteries used in the Teslas decreases.
c. The price of gasoline increases to $10.00 per gallon.
d. Workers who produce Teslas demand higher wages.