Hi karthikpandian19:

Let there be n rings expected to be sold. Then total money expected to be donated =ny. So we need to find ny.

Let's look at the statements now:

1. 80 more rings were sold than expected, so the total amount donated was $2,000 more than the expected amount.
So we have (80+n)*y=ny+2000 => 80y = 2000 => y = 25. So we know y but still don't know what n is. Not sufficient.

2. In this case, we are told n=400, we don't know what y is. Not sufficient.

Both together: First one tells us y, second tells us n. So together, we get yn. Sufficient.

So C is the answer.

Let me know if this helps

OA is C

karthikpandian19 wrote:A certain group of jewelers agreed to donate y dollars to Oxfam Charities for each engagement ring sold during a 30-day period. What was the total amount that was expected to be donated?

80 more rings were sold than expected, so the total amount donated was $2,000 more than the expected amount.
A total of 400 engagement rings were expected to be sold