Hemming Company reported the following current$-$year purchases and sales for its only product.

$\backslash$table$[[$Date$,$Activities,Units,Acquired at$,$cost$,,$Units Sold at$,$Retail$],[$January $1,$Beginning inventory,$200$ units,@$$10,=,$$$2,000,,],[$January $10,$Sales,,,,,$150$ units,@ $$40],[$March $14,$Purchase,$350$ units,$($a$)$ $$15,=,5,250,,],[$March $15,$Sales,,,,,$300$ units,@ $$40],[$July $30,$Purchase,$450$ units,@$$20,=,9,000,,],[$October $5,$Sales,,,,,$430$ units,@$$40],[$October $26,$Purchase,$100$ units,@ $$25,=,2,500,,],[$Totals$,1,100$ units,,,$$18,750,880$ units,$]]$

Ending inventory consists of $45$ units from the March $14$ purchase, $75$ units from the July $30$ purchase, and all $100$ units from the October $26$ purchase. Using the specific identification method, calculate the following.

b$)$ Gross Margin using Specific Identification