The following data were obtained from a survey of college students. The variable
X represents the number of non-assigned books read during the past six months.
x 0 1 2 3 4 5
P (X = x) 0.20 0.25 0.20 0.15 0.10 0.10

Find P(X≤3).
A.0.20.
B.0.80.
C.0.85.
D.0.15.