The half life of a certain substance is about 4 hours. the graph shows the decay of a 50 gram sample of the substance that is measured every hour for 9 hours.

a graph shows time (hours) labeled 1 to 10 on the horizontal axis and quantity (grams) on the vertical axis. a line decreases from 0 to 9.

which function can be used to determine the approximate number of grams of the sample remaining after t hours?

y = 25(0.15)t
y = 25(0.85)t
y = 50(0.15)t
y = 50(0.85)t