Answer:
71% or 0.71
Step-by-step explanation:
according to the topic
P(x = 4) = 0.31
P (x = 3) = 0.40
so a student\s grade is B or better
P (x = 4) + P (x = 3) = 0.31 + 0.40 = 0.71
so the answer is 0.71 or 71%
