Answer:
a)  ≈  9.6 years
b) Â Modified duration is a better measure because Modified duration consider the concept of negative convexity
c) i) coupon of bond = 4%
 Modified duration will increase since the coupon rate of payment decreased
ii) Maturity of bond = 7
 Modified duration will decline as Maturity period has declined to 7 years
Explanation:
A) Calculate modified duration using the preceding information
modified duration = Macaulay duration / ( 1 + (yield to maturity / 2 ))
               = 10 / ( 1 + ( 0.08 / 2 ))
               = 9.615 years
B) Modified duration is a better measure because Modified duration consider the concept of negative convexity while Macaulay methods shows the inverse relationship between the duration of the bond and coupon payment .
C) Determine Direction of change in modified duration if
i) coupon of bond = 4%
 Modified duration will increase since the coupon rate of payment decreased
ii) Maturity of bond = 7
 Modified duration will decline as Maturity period has declined to 7 years