C is the answer.........................
Is there more to this problem? By saying f(4), you'd be inputting a 4 for every variable x. There is not enough info here to answer the question.
The answer is C, 25% increase. To find the increase, subtract starting value (780) from the final value (975). It equals out to be 195. Divide 195 by the starting value which turns out to be 0.25. Then, multiply 0.25 by 100 which equals out to be 25.
Answer:
This cannot be simplified any further. That is the simplest you'll get.
