Final answer:
The monopoly's markup is 50%.
Step-by-step explanation:
To calculate the monopoly's markup, we need to first understand the relationship between price, marginal cost, and markup.
The markup can be calculated using the formula:
Markup = (Price - Marginal Cost) / Price * 100
Substituting the given values, the markup would be:
Markup = ($210 - $105) / $210 * 100 = 50%
Therefore, the monopoly's markup is 50%.