c
step-by-step explanation:
it would be see because your formula is f(x)=6x, so 6 times 1 is 6 and you go on and the best answer is c.
circle area = pi * radius^2
if diameter = 10 then radius = 5
circle area = pi * 5^2
circle area = pi * 25
circle area = 78.5398163397 square units
i use my brain for prombles like this maybe you could try it
126 maybe. sorry