Lakshmi decides to change her password on her computer and

wants to only use each character once. If she want to make her

password ten characters long, how many possible choices does

she have if

$$ she only uses lower case letters $($English alphabet$)$

$$ both upper and lower case letters

$$ includes numbers as well as case sensitive letters

How about if she doesn$$t limit herself to using each only once?

$8/10$