The exponential decay formula is:
[tex]y=a(1-r)^t[/tex]where y is the final cost, a is the initial cost, r is the annual decreasing rate (as a decimal), and t is the time in years.
Substituting with a = $60, r = 0.09, and t = 3 years, we get:
[tex]\begin{gathered} y=60\cdot(1-0.09)^3 \\ y=60\cdot(0.91)^3 \\ y=60\cdot0.75 \\ y=45.21 \end{gathered}[/tex]It will cost $45.21 in 3 years
