Aparalegal assistant processes 64 phone calls in 3 hours. what is the rate per hour?

Ithink i know it but i want to be sure so can you me out ?

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

Asinusoidal function whose frequency is 1/6pi