opacity of area

A certain negative has an area in it (call it area A) that transmits 6.25 percent of thelight. What is the opacity of area A of the negative? Another area (call it area B) ofthe same negative has an opacity of 64. In terms of factors of two, how much morelight does area B block than area A? [For this last part, we seek the following: is itone factor of two, i.e. 2; or is it two factors of two, i.e. 4, or three factors of two, i.e.8; or one factor of two less light, i.e. ½, or what?]