Rank the following isotopes in order of their radioactivity, from the most radioactive to the least radioactive: (a) nickel-59, half-life 75,000 years; (b) uranium-238, half-life 4.5 billion years; (c) actinium-225, half-life 10 days.

In november 1987, a massive iceberg broke loose from the antartic ice mass and floated free in the ocean. the chunk of ice was estimated to be 98 mi long, 25 mi wide, and 750 ft thick. a typical backyard swimming pool contains about 24,000 gallons of water. how many of these pools could you fill from the water in this iceberg? (assume the iceberg is a rectangular solid of the above dimensions and consists of water only). express answer in scientific notation.