(a) Graph f(x) = e^−x2 and shade the area represented by the improper integral ∫^∞_−∞ e^−x2 dx.
(b) Use a calculator or computer to find ∫^a_−a e^−x2 dx for a = 1, a = 2, a = 3, a = 5.

(c) The improper integral  ∫^∞_−∞ e^−x2 dx converges to a finite value. Use your answers from part (b) to estimate that value.