Answer:
The probability that there will be a total of 7 defects on four units is 0.14.
Step-by-step explanation:
A Poisson distribution describes the probability distribution of number of success in a specified time interval.
The probability distribution function for a Poisson distribution is:

Let <em>X</em> = number of defects in a unit produced.
It is provided that there are, on average, 2 defects per unit produced.
Then in 4 units the number of defects is,
.
Compute the probability of exactly 7 defects in 4 units as follows:

Thus, the probability of exactly 7 defects in 4 units is 0.14.
4 / 0.80 = 12 / x...cross multiply
4x = 0.80 * 12
4x = 9.6
x = 9.6 / 4
x = 2.4.....12 apples cost $ 2.40
B-x=3
Solve for x-
4x+1-1=13-1
4x=12
4x/4=12/4
x=3