2、Use $1, 2, 3, 4$ to form a four-digit number $\overline{a b c d}$, with the following requirements:
（1） $a, b, c, d$ are all different; （2）$b$ is greater than $a$ and $d$, and $c$ is greater than $a$ and $d$. How many such four-digit numbers are there? $\qquad$
【Analysis】From the problem, $b$ and $c$ should take $3$ and $4$, $a$ and $d$ should take $1$ and $2$, there are $2 \times 2=4$ numbers