This question is poorly-worded and can be answered with an infinite number of possibilities. This clearly is not a question involving the combined price of $4.50 per lb for a mixture of peppers and beans since that combined price would fall below the highest price, the price of beans.

We could say 1 lb of beans ($4) and 1/2 lb of peppers ($0.50) to total $4.50 or we could say 1/2 lb beans ($2) and 2.5 lbs peppers ($2.50) to total $4.50, etc.