$\backslash$table$[[$Account inquiry $($hours$),$$$78,000,2,000$ hours$],[$Account billing $($lines$),$$$41,000,20,000$ lines$],[$Account verification $($accounts$),$$$16,000,22,000$ accounts$],[$Correspondence $($letters$),$$$12,000,1,400$ letters$],[,,],[$The above activities are carried out at two of its regional offices.,Northeast Office,Midwest Office$],[$Activities$,180$ hours,$300$ hours$],[$Account inquiry $($hours$),16,000$ lines,$7,000$ lines$],[$Account billing $($lines$),1,400$ accounts,$600$ accounts$],[$Account verification $($accounts$),70$ letters,$130$ letters$],[$Correspondence $($letters$),,]]$

What is the cost per letter for the correspondence activity? $($Round your answer to the nearest cent.$)$

A$.$ $$6\mathrm{.}00$

B$.$ $$29\mathrm{.}29$

C$.$ $$8\mathrm{.}57$

D$.$ $$0\mathrm{.}73$