Jia is skipping a rock across a pond. The sequence {4.2, 3.57, 3.0345, 2.5793, …} describes the height of the rock on each successive skip. Which explicit formula describes this geometric sequence? a)an=3.57(4.2)n−1

b)an=4.2(0.85)n−1

c)an=4.2(0.15)n−1

d)an=0.85(4.2)n-1