$$A=B \times H= \frac{ 1 }{ 5 } \times \frac{ 1 }{ 4 }$$
$A=BH\text{ and }BH=\frac{1}{20}$
$H=\frac{1}{20B}$
$A=\frac{1}{20}\text{ and }B\neq 0$
$B=\frac{1}{20H}$
$A=\frac{1}{20}\text{ and }H\neq 0$
