Final answer:
The provided question lacks sufficient data to calculate the total number of radio/cd units on hand for a standard and sports model comparison. Essential details are missing, and therefore an accurate answer cannot be provided without more context.
Step-by-step explanation:
The question you've provided does not contain enough information to accurately determine the total number of radio/cd units currently on hand. Without specific details or context to the numbers like 75, 115, 190, 290, we cannot ascertain how they correspond to the standard and sports model comparison. To solve this problem, additional data would be required, such as the number of standard and sports models available, as well as the number of radio/cd units per model.