Answer
a. $0.547$
b. $0.986$
c. $0.453$
Work Step by Step
Use the Poisson formula with $\mu=8$
a. At least 8 calls
$P(X\geq8)=1-P(X\leq7)=1-0.453=0.547$
b. 3 or more calls
$P(X\geq3)=1-P(X\leq2)=1-0.014=0.986$
c. At most 7 calls
$P(X\leq7)=0.453$
