Toby skated from his house to the beach at a constant speed of 8 88 kilometers per hour, and then skated from the beach to the park at a constant speed of 7 77 kilometers per hour. The total distance Toby skated was 20 2020 kilometers, and it took him twice as long to get to the park.

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