Help please!! This problem is in Discrete mathematics
List its elements between the braces

Facial shaving brushes are either bulb-shaped or fan-shaped. an experiment is to be conducted to determine whether the lather thickness is the same for both types of shaving brushes. in previous studies, it was determined that shaving brush size (small, medium, large) is associated with lather thickness, but shaving brush type (wolf whiskers, maggard razors, frank shaving, and so on) is not associated with lather thickness. how could the experiment best be conducted? by blocking on shaving brush size by blocking on shaving brush type by blocking on shaving brush shape by blocking on lather thickness without blocking

Agroup leader is speaking to his group about the need to increase productivity. in order to avoid offending the group members, he is being vague and indirect. his comments are met with confused looks. which area of individual competence is lacking

Compare and contrast the environmental consequences of reliance on coal with reliance on petroleum.