Sol：
(a)n=1900rpm=95/3 r/s
ω=2πn=190π/3 rad/s
(b)As we know,the baseball maybe full of the wood or wool,so we can assume the baseball is a solid ball.
we will get the moment of inertia of the baseball should be:
I = ∫m/(4πR³/3)4πr²·r²dr
=(3m/R³)∫r^4dr
=(3/5)mR²
the circumference C=2πR=9.25 inches = 0.23495m
M=Iβ=I(ω-0)/t=(3/5)×0.14kg×(0.23495m)²×190π/3 /s÷0.06s=15.38N·m