Answer:
aₙ = a₁ + (n-1) * 18 a₁ = -5
Step-by-step explanation:
aₙ = a₁ + (n-1) * d a₁ = -5 d = 13 - (-5) = 18
a₂ = -5 + (2 - 1) * 18 = -5 + 18 = 13
a₃ = -5 + (3 - 1) * 18 = -5 + 36 = 31
a₄ = -5 + (4 - 1) * 18 = -5 + 54 = 49
4000 and 7000
B grade
75 + 90 + 88 + 86 = 339
339/4 = 84.75
Grade B = 80-89%