Calculating Response Factors

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1. The problem statement, all variables and given/known data

Determine the response factors for both Na and K with the Li internal standard

Concentration Ratio
Na : K : Li (in ppm)
5.0 : 5.0: 500
-------------------

Signal Ratio
Na : K : Li (relative units)
4.9 : 6.4: 36.2

2. Relevant equations

Ax/x = F(As/s)
Ax = Absorbtion signal of analyte
x = concentration of analyte
F = response factor
As = absorbtion signal of standard
s = concentration of standard

3. The attempt at a solution

Calculation for Na

(4.9)/(5.0) = F [(36.2)/(500)]
F = 13.5

Calculation for K

(6.4)/(5.0) = F [(36.2)/(500)]
F = 17.7

Seems simple enough right? So I was hoping that someone would be able to tell me if this is correct or incorrect because I have a funny feeling I did something strange (problem was too easy).
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution