ANSWER :
Rate of decay is 0.11
EXPLANATION :
The general function for growth or decay is :
[tex]f\lparen x)=P\left(1+r\right)^x[/tex]where r is the growth or decay.
r is positive if growth
r is negative if decay
From the problem, we have the function :
[tex]f\mleft(x\mright)=13500\left(0.89\right)^x[/tex]Equate the parenthesis to (1 + r)
That will be :
[tex]\begin{gathered} 0.89=1+r \\ 0.89-1=r \\ r=-0.11 \end{gathered}[/tex]Since the sign of r is negative, it is a decay function
The rate of decay is 0.11