[NTG-context] Math mode: Vertical space between cases.

Dear list. How can I increase vertical space between cases? \startformula f(x)= \startmathcases[style=\displaystyle] \NC \frac{3}{10}\;, \NC if \math{x=2} \NR \NC \frac{k+9}{6}\;, \NC if \math{x=3} \NR \NC \frac{h}{16}\;, \NC if \math{x=4} \NR \stopmathcases \stopformula