I think the data provided is insufficient as it is not only the mass or quantity of Co-60 that decides its activity but also the neuton flux and time in which it is kept for its neutron activation to take place consequent upon which it becomes radioactive.

 

Anyway u can use the concept that decay scheme of Co-60 is by emission of 2 gamma photons of energy 1.33Mev and 1.17Mev.