∴(e-xf(x))'=- e-xf(x)+e-xf'(x)
= e-x(f′(x)-f(x))& gt; 0
∴e-xf(x) is adding functions.
∫a > 0
∴e-af(a) >f(0)
∴ f (a) > EAF (0) Select B.