Answer:
a) the maximum shear stress τ the bar is 16T
  the bar is 16T /πd³
 /πd³
b) the angle of twist between the ends of the bar is 16tL² / πGd⁴  
Explanation:
 Given the data in the question, as illustrated in the image below;
d is the diameter of the prismatic bar of length AB
t is the intensity of distributed torque 
(a) Determine the maximum shear stress tmax in the bar
Maximum Applied torque  T_max = tL
we know that;
shear stress τ = 16T/πd³
where d is the diameter
so
τ = 16T
 = 16T /πd³
 /πd³
Therefore, the maximum shear stress τ the bar is 16T
  the bar is 16T /πd³
 /πd³
(b) Determine the angle of twist between the ends of the bar.
let theta ( ) be the angle of twist
) be the angle of twist
polar moment of inertia  = πd⁴/32
 = πd⁴/32
now from the second image;
lets length dx which is at distance of "x" from "B"
Torque distance x
T(x) = tx
Elemental angle twist = d = T(x)dx / G
 = T(x)dx / G
so
 d = tx.dx / G(πd⁴/32)
 = tx.dx / G(πd⁴/32)
 d = 32tx.dx / πGd⁴
 = 32tx.dx / πGd⁴
so total angle of twist  will be;
 will be;
 =
 =   
 
 =
 =   32tx.dx / πGd⁴
 32tx.dx / πGd⁴
 = 32t / πGd⁴
 = 32t / πGd⁴   
 
 = 32t / πGd⁴ [ L²/2]
 = 32t / πGd⁴ [ L²/2]
 = 16tL² / πGd⁴
 = 16tL² / πGd⁴  
Therefore,  the angle of twist between the ends of the bar is 16tL² / πGd⁴