$1.$ Give your best estimate in a human$-$readable format.

$($a$)$ How long does a brute force approach take on average to crack a key of $64$ bits using a PC that is capable of performing $1$ decryption per microsecond? $(3$ pts$)$

$($b$)$ How about using a supercomputer that is capable of performing $106106$ decryptions per microsecond? $(3$ pts$)$