Answer
See below.
Work Step by Step
Since the events are independent:
a) $P(\text{at most 2})=P(0)+P(1)+P(2)=0.1+0.15+0.2=0.45$
b) $P(\text{at least 2})=P(2)+P(3)+P(4 \ or \ more)=0.2+0.24+0.31=0.75$
c) $P(\text{at least 1})=P(1)+P(2)+P(3)+P(4 \ or \ more)=0.15+0.2+0.24+0.31=0.9$
