The price of producing a $4 chocolate bar goes up, so the seller of the chocolate bar raises the price to $5. a student describes the effect on the demand for the chocolate, saying, "since the price goes up, the quantity demanded will go up." evaluate the student's answer.

Think of it like this.  If you could get a new cell phone for ten bucks, you'd want it, right?  In fact, pretty much EVERYONE would want it.  This means the quantity demanded will be high: more people want it.  BUT, if it goes up to $1,000, I bet you wouldn't want it that badly!  The quantity demanded will go down, because less people want to buy it.  It's the same thing with the chocolate bar.  Since the price goes up, the quantity demanded will go DOWN, because less people want to buy it now that it's more expensive.  The student's answer is incorrect.

The student's answer is incorrect.  Since the price goes up, the quantity demanded will go down.