Answer: . b. 0.9
Explanation:
The general exponential decay function is given by :-
, where A is the initial valuye , r i sthe rate of decay and x is time period.
The multiplicative rate of exponential decay is given by :-

Given: the rate of decay = 10 % = 0.1
Then , the multiplier for the rate of given exponential decay will be :-

Hence, the the multiplier for the rate of given exponential decay=0.9