we have the function
f(t)=9500(0.1)^t
this is an exponential function of the form
y=a(b)^x
where
a is the initial value
b is the base of the function
In this problem
b=0.1
the value of b is less than 1
that means
b=1-r
r=1-0.1
r=0.90
the rate of change is 90%
is a decay exponential function at a rate of 90% each week