An inventory record for the bookstore of a local college shows a receipt of 150 accounting books on may 1. another shipment of 25 books arrived on june 15. on may 20, 100 books were sold to the students enrolled in the summer school class. on june 3, 31 books were purchased by the students enrolled off-campus. on june 17, a shipment of 150 books arrived. find the number on hand on june 17.

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