Runs when an agent purchases a good with money and allows the quantity passed to the function to be modified.
agent — Agent
The agent initiating the purchase.
partner — Agent
The trading partner of the agent.
good — str
The name of the good being purchased.
q — num
The quantity of the good being purchased.
p — num
The per-unit price at which the good was purchased. The purchase will involve an outlay of
Expected Return Value — tuple(num,num)
If specified, overrides the price and quantity, respectively, originally initiated.