Assuming the coin is fair (most coins are not completely fair) and that the person flipping is not able to control the tosses (some people can) then the chance is 0.125. On each flip, the chance is 1/2. The combination is simply the product of three tosses, since the events are independent.
Unit rate is (cost) per 1 unit the unit is fluid oz 'per' is fraction cost/1unit so we do 2.56/32 divide completely 2.56/32=0.08/1 the unit rate is $0.08 per oz
