4. The control rods for a certain rector are made of cadmium (10 w/o), indium (15 w/o) and silver (75 w/o). Calculate the rate at which thermal neutrons are absorbed per gram of this material at a temperature of 400 °C in 2,200 m/s flux of 5 x 1013 neutrons/cm'-sec.
[The values of ga (400°C) are 2.5589 for Cd (Cadmium), and 1.011 for In (Indium). Silver is a 1/v absorber. The absorption cross sections are 2459 b for Cd, 193.5 b for In, and 63.6 b for Ag.]