Assume a Steiner triple system exists with parameters $b, v, k, r, \lambda$, where $k=3$. Let $a$ be the remainder when $\lambda$ is divided by $6 .$ Use Theorem $10.3 .1$ to show the following:
(1) If $a=1$ or 5 , then $v$ has remainder 1 or 3 when divided by 6 .
(2) If $a=2$ or 4 , then $v$ has remainder 0 or 1 when divided by 3 .
(3) If $a=3$, then $v$ is odd.