Sam is comparing the half-life of two isotopes of uranium. The half-life of Uranium-238 is 4.5 * 10 ^ 9 years. The half-life of Uranium-233 is 1.6 * 10 ^ 5 years. He computed how much greater the half-life of Uranium-238 is than that of Uranium-233, and his calculator displayed the number 2.81E4. What is this number in scientific notation? (1 point)

2.81 * 10 ^ 4

2.81 * 10 ^ - 4

2.81 + 10 ^ 4

4 * 10 ^ 2.81