Assume that for the entire business sector of a private closed economy, there are $0 worth of investment projects that will yield an expected rate of return of 25 percent or more. but there are $15 worth of investments that will yield an expected rate of return of 20–25 percent, another $15 with an expected rate of return of 15–20 percent, and an additional $15 of investment projects in each successive rate of return range down to and including the 0–5 percent range. if the real interest rate is 5 percent, what amount of investment will be undertaken?