Answer:
The number is zero
Explanation:
From the question we are told to state the number of on-to-one that exist from the set of 5 element to the set 4 element
Generally there are no one-to-one function from a set with a higher number of elements to a set with the lower number of elements
So the correct answer to the question is there are no one-to-one function from the set of 5 elements to the set of 4 elements