Answer
$7.4\times10^{-7}\frac{Gy}{day}$.
Work Step by Step
Assume that the activity is constant. This tells us the rate at which gamma rays are emitted.
For each emitted gamma ray of energy 122 keV, 61 keV is deposited in the body.
$$(1.55\times10^{-6}Ci)(3.70\times10^{10}\frac{\gamma/s}{Ci})(86400\frac{s}{day})(\frac{61keV}{\gamma})(1.60\times10^{-16}\frac{J}{keV})(\frac{1}{65kg})$$
$$=7.4\times10^{-7}\frac{J/kg}{day}=7.4\times10^{-7}\frac{Gy}{day}$$
