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.