Every group of order $56$ has a proper non - trivial normal subgroup? I tried getting $n_{2}$ and $n_{7}$ , denote the number of Sylow-2-Subgroups and Sylow-7-Subgroups respectively.
I got two cases for $n_{2} = 1 , 7 $ and for  $n_{7} = 1 , 8$ , i noticed that if $n_{2} = 1$ and $n_{7}= 1$ ,then we are done since they are unique subgroups and hence will be normal in $G$.
Next how to proceed with the cases of $n_{2} = 7$ and $n_7 = 8$.
Please help?

Count the total number of elements. Suppose neither $n_2$ nor $n_7$ is equal to $1$. Then $n_7=8$, which makes $8\cdot 6$ elements which belong to a $7$-Sylow subgroup, and to no other Sylow subgroup.
On the other hand, since $n_2=7$, each $2$-Sylow subgroup contains at least $4$ elements which belong to no other Sylow subgroup. In all $7\cdot 4$ elements.
Summing up, the group would contain at least $48+28+1$ elements. This is more than $56$, if I'm not mistaken.
