I need help I didn't pay attention in class now I am lost.

Choose the correct classification of 3x4 − 9x3 − 3x2 + 6. 5th degree polynomial 4th degree polynomial 9th degree polynomial 24th degree polynomial

Asap! i'm not good math and i'm lost.

At store a, erasers are sold individually. the cost y of x erasers is represented by the equation y=0.75x. the costs of erasers at store b are shown in the graph.