Consider the question. Elizabeth uses $3.00 worth of ingredients to make a bag of granola. She makes 20 bags and sells them for $6.00 a bag at the farmer's market. An hour before closing, she has sold 15 bags and marks the remaining 5 bags down to $4.00 and sells them soon after. What is her net profit?
 If the answer is '50'; explain the reasoning:
She uses $3.00 of ingredients per 1 bag of granola and she makes 20 bags so she spends 3 * 20 = $60.00 on ingredients. She sells 15 bags for $6.00 so she makes 15 * 6 = $90.00. She sells her last 5 bags for $4.00 so she makes 5 * 4 = $20.00. She made $90.00 and $20.00 for a total of 90 + 20 = $110.00. She made $110.00 but spent $60.00 on ingredients so her net profit is 110 - 60 = $50.00.