Write an explicit formula for aₙ, the nᵗʰ term of the sequence 25, 20, 15, ..., 0.25, 20, 15,...
a) aₙ = 25 - 5(n-1)
b) aₙ = 25 - 5n
c) aₙ = 25 - 5n + 1
d) aₙ = 25 - 5(n+1)