Total funds available with Betsy = $50,000
Interest rate in B-rated bonds = 13% per year
Let amount invested in B-rated bonds be x
Interest rate in certificate of deposit (CD) = 5% per year
Amount invested in CD = 50,000-x
Now, we have to determine x such that Betsy can get exactly $6,000 in interest per year. Hence:
x * 13% + (50,000 - x) * 5% = 6,000
⇒ 0.13x - 0.05x + 2,500 = 6,000
⇒ 0.08x = 3,500
⇒ x = 43,750
Hence, Betsy should invest $43,750 in B-rates bonds
And 50,000 - x = 50,000 - 43,750 = 6,250
And she should invest 6,250 in CD