If the half life for strontium-90 is approximately 28 years, then what is the whole life for strontium-90? there is no answer choices plz

Directions conduct research to collect information and data in order to write a well-informed argument essay responding to the following prompt: do you believe your local power company is doing enough to reduce dependence on nonrenewable energy sources? why or why not? remember that your argument essay should contain: a claim supporting evidence connected to your claim an acknowledgement of counterclaim(s) a conclusion after writing your rough draft, reread it and edit it for spelling, grammar, and clarity.