Answer:
At approximately x = 0.08 and x = 3.92.
Step-by-step explanation:
The height of the ball is modeled by the function:

Where f(x) is the height after x seconds.
We want to determine the time(s) when the ball is 10 feet in the air.
Therefore, we will set the function equal to 10 and solve for x:

Subtracting 10 from both sides:

For simplicity, divide both sides by -1:

We will use the quadratic formula. In this case a = 16, b = -64, and c = 5. Therefore:

Substitute:

Evaluate:

Simplify the square root:

Therefore:

Simplify:

Approximate:

Therefore, the ball will reach a height of 10 feet at approximately x = 0.08 and x = 3.92.
D. Expenses for a birthday party are not a fixed expense.
By definition, a fixes expense is a bill or something that won't change in the amount of payment. A car payment will always be the same each month; the mortgage will always be the same and car insurance will always be the same each month.
Let x be a random variable representing the length of a text messaging conversation, then
P(x > 3) = 1 - P(x < 3) = 1 - P(z < (3 - 2)/0.5) = 1 - P(z < 2) = 1 - 0.97725 = 0.02275