help plss!!

Gabby Hong sels homemade knit scarves for $20 each a local crat shows. Her contrbution margin ratio is 62.5%. Currently, the crat show entrance fees cost Gabby $500 per year. The craft shows are raining their entrance fees by 105 next year. How many extra scarves will Gabby have to solt next year just to poy for nising entrance feo costs? Begn by ibentifying the general fomvla to compule the breakeven sales in units