Assume that if the interest rate that businesses must pay to borrow funds were 20 percent, it would be unprofitable for businesses to invest in new machinery and equipment so that investment would be zero. But if the interest rate were 16 percent, businesses will find it profitable to invest $10 billion. If the interest rate were 12 percent, $20 billion would be invested. Assume that total investment continues to increase by $10 billion for each successive 4 percentage point decline in the interest rate. Refer to the above graph. Which of the following is the correct graphical presentation of the indicated relationship?