The number of four digit numbers that can be formed using the digits $1,2,3,4,5,6$ and 7 which are divisible by 4 , when the repetition of any digit is not allowed,

If ${ }^m P_r-{ }^{(m-1)} p_r=a \cdot{ }^{(m-1)} P_s$, then $a-s=$

The total number of ways of selecting 4 letters from all the letters of the word TSEAMCET is

Let $a, b, c \in N$ and $a+b+c=5$. Let $L, M$ be the least and greatest values of $2^a 3^b 5^c$, respectively. Then $M-L=$