Tính giá trị các biểu thức sau:
a. $A={\left(\frac{1}{27}\right)}^{-\frac{2}{3}}+{\left(\frac{1}{16}\right)}^{-1,25}$
b. $B=\frac{3^4.3^{-2}+2^5.2^{-4}}{2^4.2^3-2.3^5.3^{-4}}$
c. $C=\frac{3^5.{\left(\frac{1}{3}\right)}^3+{\left(2^2\right)}^{-3}{\left(\frac{1}{4}\right)}^{-4}}{5^{-3}.25^2+{\left(\frac{3}{2}\right)}^0{\left(\frac{1}{25}\right)}^{-1}}$