According to the law of demand, as the price of a good increases, the quantity demanded typically decreases, assuming all other factors remain constant. If the price of lattes increases from $4 to $5, Mark would likely buy fewer lattes than before.
However, without specific information on how much Mark was buying at the $4 price point and how that quantity changes with the new price, it's impossible to determine the exact quantity he would be willing to buy. Generally, if lattes were previously affordable at $4, a price increase to $5 could lead him to buy less, but we cannot definitively select from the options without more context.
If you have additional information about Mark's demand at the previous price, that would help clarify his response to the price change.
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