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Explanation / Answer

You are going to use the equation with Boltzmann's constant (kB) for this

average kinetic energy is equal to (3/2)*kB*T

this is also equal to 1/2*m*v^2

so 3/2*kB*T = 1/2*m*v^2, which solving for v we get v = sqrt(3*kB*T/m)

kB is 1.38*10^-23

T is your 130nK which is 130*10^-9 K

for m, you have the mass in amu. You need to convert this to kg. 1 amu is 1.66*10^-27 kg

m = 86.91 amu * 1.66*10^-27 (kg/amu)

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