Step 1: Understanding the question.
The customers who bought a 250ml bottle are assigned numbers from 501 to 1000, and prizes are awarded to customers whose ticket number is divisible by 5 or 7. We need to find the number of customers who bought a 250ml bottle but did not get a prize.
Step 2: Number of customers who bought a 250ml bottle.
There are 500 customers who bought a 250ml bottle, as the tickets numbered 501 to 1000 were distributed among them.
Step 3: Number of customers awarded a prize.
The customers who have ticket numbers divisible by 5 or 7 are awarded a prize. To find the number of such customers, we use the principle of inclusion and exclusion:
- Number of customers whose tickets are divisible by 5 = \( \left\lfloor \frac{1000}{5} \right\rfloor - \left\lfloor \frac{500}{5} \right\rfloor = 200 - 100 = 100 \)
- Number of customers whose tickets are divisible by 7 = \( \left\lfloor \frac{1000}{7} \right\rfloor - \left\lfloor \frac{500}{7} \right\rfloor = 142 - 71 = 71 \)
- Number of customers whose tickets are divisible by both 5 and 7 (i.e., divisible by 35) = \( \left\lfloor \frac{1000}{35} \right\rfloor - \left\lfloor \frac{500}{35} \right\rfloor = 28 - 14 = 14 \)
Using the inclusion-exclusion principle:
\[
\text{Total awarded} = 100 + 71 - 14 = 157
\]
Step 4: Number of customers who bought 250ml bottle but were not awarded a prize.
The total number of customers who bought a 250ml bottle is 500. The number of customers who were awarded a prize is 157. Therefore, the number of customers who bought a 250ml bottle but were not awarded a prize is:
\[
500 - 157 = 343
\]
Step 5: Conclusion.
The correct answer is (B) 536 customers who bought a 250ml bottle but were not awarded a prize.