Which of the following represents the left-hand sum approximation of the area under the curve?
a) ∫[a,b] f(x) dx
b) lim(n→[infinity]) Σ[i=1,n] f(xi*) Δx
c) lim(n→[infinity]) Σ[i=0,n-1] f(xi) Δx
d) lim(n→[infinity]) Σ[i=1,n] f(xi) Δx