Investing in Bonds A woman wishes to invest $
12
,
000
in three types of bonds: municipal bonds paying
7
%
interest per year, bank certificates paying
8
%
, and high-risk bonds paying
12
%
. For tax reasons she wants the amount invested in municipal bonds to be at least three times the amount invested in bank certificates. To keep her level of risk manageable, she will invest no more than $
2000
in high-risk bonds. How much should she invest in each type of bond to maximize her annual interest yield? [Hint: Let
x
=
amount in municipal bonds and
y
=
amount in bank certificates. Then the high-risk bonds will be
12
,
000
−
x
−
y
.]