A sealed source contains 0.50 g of radium-226 (atomic mass = 226 g mol⁻¹; half-life = 1600 y).
(i) Calculate the initial activity of the source in curie.
(ii) Determine its activity in becquerel after 4800 y of storage.
(iii) What mass of radium-226 would be needed today to obtain an activity of 1.00 × 10⁶ Bq?
(iv) Comment briefly on the practical difficulty, if any, in handling a source whose activity is measured in curie.