The half-life of strontium-90 is 25 years. Find the amount of strontium-90 remaining after 10 years if q₀ = 98 kg.

In use the fact that the quantity of a radioactive substance after t years is given by q = q₀(2^-t/k), where q₀ is the original amount of radioactive material and k is its half-life (the number of years it takes for half the radioactive substance to decay).