Final answer:
The amount of cash collected from customers was $3,100.
Step-by-step explanation:
To determine the amount of cash collected from customers, we need to calculate the change in accounts receivable. The beginning balance was $600, credit sales were $3,200, and $200 was written off. So, the change in accounts receivable is ($600 + $3,200 - $200) - $500 = $3,100. Therefore, the correct answer is option a) $3,100.