Heat current will flow from $A$ to $B$ via path $ACB$ and $ADB$ . Since all the rod are identical so ($\Delta \theta_{AC} > \Delta \theta_{AD}$
(Because heat current $H = \frac{{\Delta \theta }}{R};$here R = same for all.)
==> ${\theta _A} - {\theta _C} = {\theta _A} - {\theta _D}$ ==> ${\theta _C} = {\theta _D}$
i.e. temperature difference between $C$ and $D$ will be zero.
(Take Stefan-Boltzmann constant $=5.67 \times 10^{-8} Wm ^{-2} K ^{-4}$, Wien's displacement constant $=2.90 \times 10^{-3} m - K$, Planck's constant $=6.63 \times 10^{-34} Js$, speed of light in vacuum $=3.00 \times 10^8 ms ^{-1}$ )-
$(A)$ power radiated by the filament is in the range $642 W$ to $645 W$
$(B)$ radiated power entering into one eye of the observer is in the range $3.15 \times 10^{-8} W$ to $3.25 \times 10^{-8} W$
$(C)$ the wavelength corresponding to the maximum intensity of light is $1160 nm$
$(D)$ taking the average wavelength of emitted radiation to be $1740 nm$, the total number of photons entering per second into one eye of the observer is in the range $2.75 \times 10^{11}$ to $2.85 \times 10^{11}$