Answer
λ = 332 pm = c
Work Step by Step
Wavelength, λ = $\frac{h}{mv}$
h = $6.626\times10^{-34}Js$
m = $9.109\times10^{-31}kg$
v = $2.19\times10^{6}m/s$
λ = $\frac{6.626\times10^{-34}Js}{9.109\times10^{-31}kg\times2.19\times10^{6}m/s}$ = $3.32\times10^{-10}m$ = 332 pm ( Value of the prefix 'pico' = $10^{-12}$)
Circumference, c = 2πr
r = 52.9 pm (given)
Then, c = $2π\times52.9 pm$ = 332 pm
Circumference and wavelength are equal.
