Answer:
3.60%
2.81%
Explanation:
The pretax cost of debt can be derived from rate excel function as shown below:
=rate(nper,pmt,-pv,fv)
nper is the number of semiannual coupons of the bond i.e 28 years*2=56 coupons
pmt is the semiannual coupon amount=$1000*4%*6/12=$20
pv is the current bond's price=$1000*107%=$1070
fv is the face value of the bond=$1000
=rate(56,20,-1070,1000)=1.80%
semiannual pretax cost of debt is1.80%
annual pretax cost of debt=1.80% *2=3.60%
after tax cost of debt=3.60%*(1-22%)=2.81%