# Combinations from two different groups

I was asking myself the next scenario but I cant figure it out how to solve it. We have two group, first one with next characters:

qwerasdf

And the second one with:

zxcdvbnr

If a have to create a string with a substring of three characters from the first group and four characters from the second one (order doesnt matter) and this string cant have repeated characters, how many combinations can be generated?.

For example, a possible solution which is ok: asdzxcv (three characters of the first group and four for the second, without any character repeated)

a wrong solution: qwrvbnr (three for the first group and four for the second one, but this time final answer have a repeated character, which is not ok).

I know how to solve when both groups have no common characters, but not this case.

$\underline{Hint}$
qweasf$\quad\leftarrow$ dr$\rightarrow\quad$ zxcvbn