Final answer:
Without specific sales figures for each year, it is not possible to calculate the total number of mobile phones sold in three years.
Step-by-step explanation:
The question pertains to calculating the total number of mobile phones sold over a period of three years. However, the information provided does not include direct sales data for the phones. Instead, it discusses probability distributions, sample sizes, user demographics, and the global scale of mobile phone usage. To accurately calculate the total sales, we would need specific sales figures for each of the three years or an average yearly sales figure that we can multiply by three. Without this data, we cannot compute the total number of mobile phones sold in the three years. If sales figures were provided, the calculation would simply involve adding the number of phones sold each year or multiplying the average yearly sales by three.