Express the fractions in each of the following sets as equivalent fractions having the least common denominator
a. $\frac{1}{4^{\prime}}, \frac{3}{16}, \frac{9}{32}$
c. $\frac{7}{10}, \frac{3}{4}, \frac{9}{25}, \frac{13}{20}$
b. $\frac{7}{16}, \frac{5}{32}, \frac{9}{64}$