A triangle is formed by $X$-axis, $Y$-axis and the line $3 x + 4 y = 60$. Then the number of points $P ( a , b )$ which lie strictly inside the triangle, where $a$ is an integer and $b$ is a multiple of $a$, is $\_\_\_\_$.
A triangle is formed by $X$-axis, $Y$-axis and the line $3 x + 4 y = 60$. Then the number of points $P ( a , b )$ which lie strictly inside the triangle, where $a$ is an integer and $b$ is a multiple of $a$, is $\_\_\_\_$.