Help!
Initially there are 6x10^9 radioactive of element W (decay constant 0.173/day) in a sample. As a nucleus of W decays, it converts 2.67x10^-28 kg of its mass to energy and releases the energy. How much time (in days) is required for the sample to releae a total of 7.2x10^-4J?
0
0.000290
0.00571
0.00943
0.0137
0.0290
0.0571
0.290
0.571
3.29
Please help, I don't even know where to start. :(