How I can test if price elasticity in a quantile regression differs among quantiles?

Dear statalists,

I would like to ask you how I could test if price elasticity differs statisticall ysignificantly between quantiles. For example after running

Code:

xtqreg lnq lnp, i(id) q(0.25)

and then

Code:

xtqreg lnq lnp, i(id) q(0.50)

and

Code:

xtqreg lnq lnp, i(id) q(0.75)

, could I test if price elasticity coefficients differ?
Thanks a lot in advance.

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