The first four terms of an arithmetic sequence are 28, 20, 12, and 4. which term of the sequence is -36

For an arithmetic sequence, the nth term is the first term plus (n-1)×the differece
the first term is 28, the difference between each adjacent number is 8
so -36=(28)+8(n-1)
8(n-1)=64
n-1=8
n=9
the 9th term is -36