Answer:
Retired woman needs to invest $13,750 into 15% bonds and 56,250 into 7% CD to meet exactly $6,000 annual return.
Please, note that this calculation is assuming only first year or linear returns as the answer would get more sophisticated if the bonds/CDs terms would include perpetuity terms, compound interest etc.
Step-by-step explanation:
Two equations to be linked:
(1) 0.15*x + 0.07*y = 6,000
(2) x + y = 70,000
Resolving the linkage:
(2) x = 70,000 - y
(1) 0.15 * (70,000 - y) + 0.07*y = 6,000
0.15*70,000 - 0.15*y + 0.07*y = 6,000
0.08*y = 10,500 - 6,000
0.08*y = 4,500
y = 56,250
(2) x = 13,750