Answer is 8671/6 which is the third choice
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Work Shown:
Find the first term of the sequence by plugging in n = 1
a_n = (5/6)*n + 1/3
a_1 = (5/6)*1 + 1/3 replace n with 1
a_1 = 5/6 + 1/3
a_1 = 5/6 + 2/6
a_1 = 7/6
Repeat for n = 58 to get the 58th term
a_n = (5/6)*n + 1/3
a_58 = (5/6)*58 + 1/3 replace n with 58
a_58 = (5/6)*(58/1) + 1/3
a_58 = (5*58)/(6*1) + 1/3
a_58 = 290/6 + 1/3
a_58 = 145/3 + 1/3
a_58 = 146/3
Now we can use the s_n formula below with n = 58
s_n = (n/2)*(a_1 + a_n)
s_58 = (58/2)*(a_1 + a_58) replace n with 58
s_58 = (58/2)*(7/6 + a_58) replace a_1 with 7/6
s_58 = (58/2)*(7/6 + 146/3) replace a_58 with 146/3
s_58 = (58/2)*(7/6 + 292/6)
s_58 = (58/2)*(299/6)
s_58 = (58*299)/(2*6)
s_58 = 17342/12
s_58 = 8671/6
