In the hydrogen spectrum, $$\lambda$$ be the wavelength of first transition line of Lyman series. The wavelength difference will be "a$$\lambda$$'' between the wavelength of $$3^{\text {rd }}$$ transition line of Paschen series and that of $$2^{\text {nd }}$$ transition line of Balmer series where $$\mathrm{a}=$$ ___________.

In the circuit shown below, maximum zener diode current will be _________ $$\mathrm{mA}$$.