Chemistry help plz!!!

[gigi9]

Can someone please help me to do the problem below? I tried to worked it out but I got (D) as the answer, but the book answer is (C)
Please help me out. Thank you very much for your time.

When solid potassium iodide is combined with flourine gas, a compound is formed that is 27% chlorine and 73%fluorine. What is the empirical formula of the compound?
A) ClF
B) ClF2
C) ClF3
D) ClF5
E) ClF7

[Adam]

How many times does 27 fit into 73? Very roughly, three. It's a three to one ratio of components. Three parts F, to one part Cl.

[HallsofIvy]

But if "solid potassium iodide is combined with flourine gas" where in the world does the chlorine come from?