Answer:
The answer is letter d
Explanation:
This problem is a basic combinatory statistical problem:
Right now Washington uses 3 numerical digits (ranging from 0 to 9 each) and three letters (ranging from A to Z). So each number can be one in 10 and each letter can be one in 26 (the amount of numbers that the alphabet has).
Given n= the amount of possible licence plates and a= the amount of numbers ranging from 0 to 9 (10 possibilities) and b= the amount of letters ranging from A to Z (26 possibilities)
n=a*a*a*b*b*b=17.576.000
So if we switch one a to a b, we increment the amount of possible outputs, that is why when switching all the numbers to letters we exponentially increase the amount of possible license plantes.