Phil's Army Surplus calculator business was going great guns $-$ especially the newest models with exclusive camouflage color schemes. Phil sold the calculators from his own dedicated web site:

Philthe$-$bill.com and had consistent sales of $510$ units per week. The calculators sold for $$42$ earning Phil a margin of $42\%$ percent on sales that originated on his site.

One source for some of Phil's sales were clickthroughs from an online department store,

BigMuddy.com. Sales originating from BigMuddy had the same retail price, but BigMuddy earned a $17\%$ commission on thoses sales. Sales based on BigMuddy clickthroughs accounted for $18\%$ of total unit sales and somewhat less of dollar sales after commissions were paid.

If Phil offers an electronic coupon for $10\%$ off the price of sales through BigMuddy and BigMuddy's dollar margins remain unchanged, what unit increase will be required to increase weekly contribution dollars from BigMuddy sales by $25\%?$ Assume zero cannibalization. units