What are the first five partial sums of the arithmetic sequence an = 0.05(n – 1) – 0.6?

The sum of the arithmetic sequence given by
an = 0.05(n – 1) – 0.6
will be given by:
a1=0.05(1-1)-0.6=-0.6
a2=0.05(2-1)-0.6=-0.55
a3=0.05(3-1)-0.6=-0.5
a4=0.05(4-1)-0.6=-0.45
a5=0.05(5-1)-0.6=-0.4
thus the summation will be:
-0.6+(-0.55)+(-0.5)+(-0.45)+(-0.4)
=-2.5
hence
S5=-2.5

Ithink it is15not sure tho