Chapter 6 - Section 6.3 - Assess Your Understanding - Vocabulary and Skill Building - Page 351: 9b

$P(x\lt4)=0.994$

$P(x\lt4)=P(0)+P(1)+P(2)+P(3)=\frac{(0.07\times10)^{0}}{0!}e^{-0.07\times10}+\frac{(0.07\times10)^{1}}{1!}e^{-0.07\times10}+\frac{(0.07\times10)^{2}}{2!}e^{-0.07\times10}+\frac{(0.07\times10)^{3}}{3!}e^{-0.07\times10}=\frac{1}{1}e^{-0.7}+\frac{0.7}{1}e^{-0.7}+\frac{0.49}{2}e^{-0.7}+\frac{0.343}{6}e^{-0.7}=0.994$