Answer:
f with an exponent of 4 f to the 4th power
Explanation:
there are four f's multiplied by each other and an exponent just shows how many of a certain thing is multiplied by itself so if I had two to the third power it would be 2 times 2 times 2 so in the equation it has 4S multiplied by each other so it would be f to the 4th power