An exam is given to students in an introductory statistics course. What is likely to be true

Question:

An exam is given to students in an introductory statistics course. What is likely to be true of the shape of the histogram of scores if:
a. the exam is quite easy?
b. the exam is quite difficult?
c. half the students in the class have had calculus, the other half have had no prior college math courses, and the exam emphasizes mathematical manipulation? Explain your reasoning in each case.