Find the exponential function that satisfies the given conditions:
Initial value = 66, decreasing at a rate of 0.5% per week (5 points)

f(t) = 0.5 ⋅ 0.34t
f(t) = 66 ⋅ 1.5t
f(t) = 66 ⋅ 0.995t
f(t) = 66 ⋅ 1.005t