Tim needs gas, Because of the mixed market the people get to chose so competition drive prices down and the government can control it if it is to high or low and lets Tim get a affordable price on gas.
When Tim decides to travel abroad he decides go to Iraq
Because of the command market in Iraq the price are mostly solid as the government tell who to produce what such as suits.
on his trip he also goes to New Zealand
In this free market it is only the people, this choice of the people is unbiased and they can chose what ever so the producer needs to meet there need better than the competition.
The procurer get to decide how many and for how much they will sell products for when shortages of a product are created they become more valuable but less people buy it.