Subway, selling sandwiches, is located on a busy corner near many other businesses. Their busiest time is at mid$-$day. Rent for the location is $$830$ per month and wages amount to $$3,775$ per month. Variable costs consist of supplies and sandwich ingredients that cost $$2\mathrm{.}25$ per sandwich. The sandwiches are sold at a price of $$8\mathrm{.}85$ each.

a$.$ How many sandwiches must they sell to break even?

b$.$ If the variable costs increase by $$0\mathrm{.}20$ per sandwich, how many sandwiches must they sell to break even?

c$.$ If the rent increases by $$207\mathrm{.}50,$ what would their profit be if they sold $1,490$ units?