A company that manufactures high-strength epoxys is considering investing $100,000 in two new adhesives identified as X and Z. The investment in X is $20,000 and is expected to yield a rate of return of 40% per year. Your supervisor asked you to determine what rate of return would be required on the remaining $80,000 in order for the total return to be at least 25%. You responded that the return would have to be at least: (a) 10.4% (b) 16.8% (c) 21.3% (d) 24.1%