The inventory records for Radford Company reflected the following

Beginning inventory on May $11,700$ units @ $$5\mathrm{.}00$

First purchase on May $71,800$ units @ $$5\mathrm{.}20$

second purchase on May $172,000$ units @ $$5\mathrm{.}30$

Third purchase on May $231,600$ units @ $$5\mathrm{.}40$

Sales on May $315,400$ units @ $$6\mathrm{.}90$

What is the weighted average cost per unit for May?