$h$ is an exponential function of the form $h(n)=a\cdot r^n$ $(r>0)$. The table below lists a few values of $h$. **What is the initial value $a$ of the function $h\ $**? $a=$ [[☃ math-keypad 1]] $n$ | $h(n)$ - | - | - $1$| $-\dfrac{1}{12}$ $2$ | $-\dfrac{1}{4}$ $3$ | $-\dfrac{3}{4}$