are as follows: average sales price per sandwich: $12.75; yearly rent: $12,000; monthly fixed utility bill: $800; average cost of ingredients per sandwich: $3.55; monthly labour bill (fixed): $10,500; miscellaneous fixed supplies/month: $1,000; misc. variable supplies: $0.37 per sandwich. How many additional sandwiches does she need to sell per month to breakeven on an advertising campaign costing $1,800 per month?