If f(x)=1x1/2+x1/3f(x) = \frac{1}{x^{1/2} + x^{1/3}}f(x)=x1/2+x1/31, evaluate f(64)f(64)f(64).
1/121/121/12
1/81/81/8
1/161/161/16
1/201/201/20