Julia bought a new car for $12,000. The car will likely depreciate 15% each year. After a certain number of years, the car will be worth $8670. According to the formula 12,000⋅(0.85)ᵗ=8670, how many years, t, will it take for the car's value to decrease to $8670?
a) 3
b) 4
c) 5
d) 6