Answer:
B
Step-by-step explanation:
Answer:
11.42 boxes
Step-by-step explanation:
For the first box bought, there is a 100% chance of getting a unique toy (since you still don't have any). E₁ = 1.
After that, there is a 4 in 5 chance of getting a unique toy from the next box, the expected number of boxes required is:

For the next unique toy, there is now a 3 in 5 chance of getting it:

Following that logic, there is a 2 in 5 chance of getting the 4th unique toy:

Finally, there is a 1 in 5 chance to get the last unique toy:

The expected number of boxes to obtain a full set is:

D,The volume will be 1/8 times the volume.
Given equation : y=ax^2
Taking a to the other side we have, x^2=(1/a)*y
This equation describes a parabola that opens up.
When a is negative, the focus is on the negative y-axis, therefore, the parabola opens down.
The answer is a. down.