Answer:
(A) 6.2 N and 20.52 N
 (B) I = 0.035 kg m^{2}
Explanation:
mass of first book (M1) = 2.1
mass of second book (M2) = 3 kg
diameter of pulley = 0.17 m
distance (s) = 1.2 m
time = 0.9 secs
(A) what is the tension in each part of the cord
     we first have to get the acceleration of the first  book 
  s = ut + 0.5 at^{2}
  since the books are initially at rest u = 0
s = 0.5 at^{2}
1.2 = 0.5 x a x 0.9^{2}
a = 2.96 m/s^[2}
        T1 = 2.1 x 2.96 = 6.2 N
-  Tension at T2 = m x ( g - a )
           (g-a) is the net acceleration of the first book
            T2 = 3 x ( 9.8 - 2.96 ) = 20.52 N
(B)  What is the moment of inertia of the pulley?
      taking clockwise rotation of the pulley to be negative while 
      anticlockwise to be positive, we can see from the diagram that T1       
      causes a clockwise rotation while T2 produces an anticlockwise rotation
        ( T2 - T1 )r = I∝
          where ∝ is the angular acceleration of the pulley relative to its radial  
          acceleration, ∝ = \frac{a}{r}
           ( T2 - T1 )r = I\frac{a}{r}
           I = \frac{(T2 - T1)r^{2}}{a}
           I = \frac{(20.52 - 6.2)0.085^{2}}{2.96}
           I = 0.035 kg m^{2}