As a department manager, Aoki worked out a plan with her team and helped set goals for each of her employees to increase their productivity. However, each employee ended up with at least $15$ goals. Which of the following criteria for effective goal setting did she violate?

a$.$ Goals should be specific and measurable.

b$.$ Goals should cover only the key result areas.

c$.$ Goals should be challenging but realistic.

d$.$ Goals should have a defined time frame.