4. Consider the set $M$ of integers $n \in[-30 ; 100]$, for which the expression $A=n^{3}+4 n^{2}+n-6$ is divisible by 5. How many integers are contained in $M$? Find the largest and smallest of them.
Answer: 1) 78 numbers; 2) $n_{\min }=-29, n_{\max }=98$.