Write the explicit rule
a1=5 d=4

Let a_1 = 5

Let d = 5 = common difference

S_n = a_1 + (n - 1)d

S_n = 5 + (n - 1)4

the answer is 0.3175 hope that you ^w^

also you might actually want to put this picture up if you want people to solve it luckily i remember this question