Final answer:
Without the necessary context or data, it's not possible to determine the total number of units available for sale or to solve the statistical problems mentioned. Specific quantitative details are needed to perform any statistical or mathematical calculations.
Step-by-step explanation:
The question does not provide enough context or data to determine the total number of units available for sale after three purchases. To accurately calculate the total number of units, we would need specific information regarding the initial number of units and the quantities involved in each of the three purchases.
Similarly, the question referring to a sample of 200 students and the expectation for them to receive $250 or more needs more context or a full data set to provide a meaningful calculation or estimation.
Regarding the car salespersons and the square footage data, these would be examples of a statistical or mathematical problem that could be solved if the complete data set and the question were provided. For meaningful answers in statistics, adequate information like the range, mean, and mode can be crucial.
For any exercises relating to total product, total cost, or total revenue, it's essential to have the requisite data like unit costs, the sales price, or the number of units produced or sold to compute the final values.