Which of the following is the correct expression for: 2/3 times the sum of 2/8 and 4/8

Group of answer choices

a. 2/3-(2/8+4/8)

b. 2/3∙(2/8+4/8)

c. 2/3∙(2/8-4/8)

d. 2/3∙2/8+4/8

Carl's candies has determined that a candy bar measuring 3 inches long has a z-score of +1 and a candy bar measuring 3.75 inches long has a z-score of +2. what is the standard deviation of the length of candy bars produced at carl's candies?