Armor-piercing shells with depleted uranium cores are fired by aircraft at tanks. (The high density of the uranium makes them effective.) The uranium is called depleted because it has had its ²³⁵U removed for reactor use and is nearly pure ²³⁸U. Depleted uranium has been erroneously called non-radioactive. To demonstrate that this is wrong:

(a) Calculate the activity of 60.0 g of pure ²³⁸U.

(b) Calculate the activity of 60.0 g of natural uranium, neglecting the ²³⁴U and all daughter nuclides.