Joanne sells silk-screened T-shirts at community festivals and craft fairs. Her marginal cost to produce one T-shirt is $ 5.50 . Her total cost to produce 40 T-shirts is $ 270 comma and she sells them for $9 each. a. Find the linear cost function for Joanne's T-shirt production. b. How many T-shirts must she produce and sell in order to break even? c. How many T-shirts must she produce and sell to make a profit of $700?