Containers of ice cream are sold by volume, not by weight. some ice cream manufacturers pump air into the ice cream before packaging it. why does this practice make the ice cream more expensive to the consumer? a) air weighs more than ice cream does. b) air weighs less than ice cream does. c) after air is pumped into ice cream, the mixture occupies a greater volume than the ice cream alone did. d) after air is pumped into ice cream, the mixture occupies a smaller volume than the ice cream alone did.