Heat and Thermodynamics

A small object is placed at the center of a large evacuated hollow spherical container. Assume that the container is maintained at 0K. At time t=0, the temperature of the object is 200K. The temperature of the object becomes 100K at t=t1 and 50K at t=t2. Assume the object and the container to be ideal black bodies. The heat capacity of the object does not depend on temperature. The ratio (t2/t1) is_________________.