At an elementary school carnival, students can draw a rubber duck out of a tub of water. Each duck has a number written on the bottom of it which correlates with a prize. There are a total of 8 ducks in the tub. Two ducks have a 5 on them, four ducks have a 6 on them, and two duck has a 7 on it. What is the expected value of a duck?
a. 8.25
b. 6.85
c. 25
d. 4
Please help!!!!