Copies at the local library cost $0.15 each. a new cooler costs $200 and it costs $0.02 to make a copy. how many copies would have to be made for the cost of making your own copies to be equal to the cost of copying at the library

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z