The four sides of a printed circuit board (PCB) enclosure consist of two pieces selected from a population whose mean length is 30 cm with standard deviation 0.14, and two pieces selected from a population whose mean length is 45 cm with standard deviation 0.31 cm. Assuming the four pieces are chosen independently, the standard deviation of the perimeter is

Step-by-step explanation:

let X1,X2 represents the length of two pieces selected from a population

the mean and standaerd deviation for the length of these two pieces X1,X2 is 30 cm and 0.14 cm

let X2,X3 represents the length of two pieces selected from a population

the mean and standaerd deviation for the length of these two pieces X2,X3 is 45 cm and 0.31 cm

To be continued on the attachment: