а) <span>(101, 103), (107, 109), (137, 139)</span>
<span>б)</span><span>(311, 313), (347, 349),</span>
<span>в) (419, 421), (431, 433), (461, 463)</span>
<span>г)</span><span>(617, 619),</span><span> (641, 643), (659, 661)</span>