For a particular analyte, a calibration line has been determined as
A=(1.52±0.05)c+(0.010±0.003),
where A is absorbance and c is concentration in mM. An unknown solution gives an absorbance of 0.678±0.005. Assuming uncertainties are independent and propagated by standard error analysis, which of the following best states the concentration of the unknown with its combined standard uncertainty?
a) (0.439±0.004) mM
b) (0.439±0.015) mM
c) (0.453±0.015) mM
d) (0.669±0.015) mM