Answer:
The base of the exponential function is 0.90
Explanation:
we know that 
The exponential function that models this situation is equal to 
 
 
where 
V is the depreciated value 
P is the original value 
r is the rate of depreciation in decimal 
x is Number of Time Periods 
in this problem we have 
 
 
 
substitute
 
 
 
 
therefore
The base of the exponential function is 0.90