To solve this problem, we use poisson distribution. The Poisson probability formula is P(X=k)=‌
λke−λ
k!
Here, λ=‌ average number of events ‌=4 K= number of events (customer) So, probability that more than 2 customers visit the shop in a specific hour =P(X>2) ‌=1−P(X≤2)=1−[P(X=0)+P(X=1)+P(X=2)] ‌=1−[‌