30. $\mathrm{P}$ is the set $\{1,2,3, \ldots, 14,15\}$. If $\mathrm{A}=\left\{a_{1}, a_{2}, a_{3}\right\}$ is a subset of $\mathrm{P}$ where $a_{1}<a_{2}<a_{3}$ such that $a_{1}+6 \leq a_{2}+3 \leq a_{3}$. How many such subsets are there of P?