Answer:
Step-by-step explanation:
An exponential function is of the form
where a is the initial value and b is the growth/decay rate. Our initial value is 64. That's easy to plug in. It goes in for a. So the first choice is out. Considering b now...
If the rate is decreasing at .5% per week, this means it still retains a rate of
100% - .5% = 99.5%
which is .995 in decimal form.
b is a rate of decay when it is greater than 0 but less than 1; b is a growth rate when it is greater than 1. .995 is less than 1 so it is a rate of decay. The exponential function is, in terms of t,