Answer
$16^{10} + 16^{26} + 16^{58}$
Work Step by Step
There are 16 hexadecimal digits. Therefore, for each place we have 16 choices.
For 10 Hexadecimal digits we have $16^{10}$ choices.
For 26 Hexadecimal digits we have $16^{26}$ choices.
For 58 Hexadecimal digits we have $16^{58}$ choices.
Applying sum rule we get, $16^{10} + 16^{26} + 16^{58}$ choices.
