Sophie's Toy Factory is considering improving the quality of the paint it uses to color dolls' faces and hands. This new paint dries more quickly and we could therefore increase its productivity. However, this new paint costs $3.60 per doll while the current paint costs $3.50 per doll. Assume that with the current paint, she makes 240 per work day (10 hours), and that with the new paint, she could make 300 per day. The cost of materials per doll would increase (from $3.50 to $3.60 per doll) but other costs would remain the same (Sophie's salary at $100/day, energy and other resources at $20 per day). If the factory adopted the new paint, Sophie's productivity

options: 

a. would increase 

b. would decrease 

c. would remain unchanged