Answer:
The answer is: No, Charley is not maximizing his utility.
Explanation:
In order for Charley to maximize his utility he should be buying only additional soft drinks.
A soft drink has a marginal utility of $50 and it costs $3. For every dollar Charley spends on an additional soft drink his utility will be $16.67.
A pizza slice has a marginal utility of $30 and it costs of $2. So for every dollar Charley spends on an additional slice of pizza his utility will be $15.