see attach

mv²/r = Ze²/4πεr² and solve for r to get:

r = Ze²/4πεmv²

You are given the equation, mvr = nh/2π, solve for r to get:

r = nh/2πmv

equate both r together to get:

Ze²/4πεmv² = nh/2πmv

solve for v

v = Ze²/2εnh
for lithium Z=3
v=3*(1.6*10^-19)^2/2*(8.85*10^-12)(6.6*10^-34)*2
v=3.28*10^6 m/s
no of revolution=v/2pir
radius of the orbit =.529*n^2*10^-10/Z
=.529*(2)^2*10^-10/3
=.705*10^-10 m
3.28*10^-6/.705*10^-10
=4.65*10^4 revolution per second