In the following problem, what is the correct constraint?
You are in the business of baking bread and cake. A loaf of bread is sold for S2 and a cake for $3. Bread takes 5 minutes and cake takes 4 minutes. Bread takes 0.15 pound of flower dough and cake takes 0.6 pound. You have 6 2/3 hours of labor and 43.2 pounds of flower dough.

a. 5x + 4y = 6 2/3
b. Maximizing 2x + 3y
c. 5x + 4y = 400
d. 1.5x+6y= 432