Why does it need "semi-colon"?
In one study, Burger set up a booth at a campus and sold cupcakes. Some customers who approached the table were told that the cupcakes cost 75 cents each. Others were told that they cost a dollar; but then, before they could respond, the price was reduced to 75 cents.
Why does it need "semi-colon" between the sentence "they cost a dollar" and the conjunction "but".
It always makes me hard.
Please help me!!