To find the total storage of the mobile phone after purchasing the additional bytes, you need to add the current storage to the additional bytes.
Current storage:
\[ 1.28 \times 10^{11} \text{ bytes} \]
Additional storage:
\[ 384,000,000,000 \text{ bytes} = 3.84 \times 10^{11} \text{ bytes} \]
Now, let's add these two values:
\[ 1.28 \times 10^{11} + 3.84 \times 10^{11} \]
To do this, you can keep them in the same power of ten:
\[ (1.28 + 3.84) \times 10^{11} = 5.12 \times 10^{11} \text{ bytes} \]
Thus, if you buy the additional bytes, your phone would have:
\[ \text{Total Storage} = 5.12 \times 10^{11} \text{ bytes} \]
The correct answer is: 5.12×10^11.