Maximum photocurrent ejected by electrons in photoelectric effect

[Mola]

Does anyone know how to determine the maximum photocurrent that could be produced by ejected electrons in a photoelectric effect experiment_(as unpolarized beam of light incidents on a metal surface)?
I don't know of any formula that calculates the photocurrent and I could not derive any. I was given Power as 28.0mW; frequency of the beam is 7.4* 10^14Hz; and stopping potential Vs as 1.45V.
- I calculated the wavelength of the beam of light as 405nm.(c/f);
- Energy in the photon as 3.06eV. (hf)
-Max speed of the electrons ejected as 7.1*10^5m/s. [sqrt(2K.E_max/mass)]
-Work function as 1.61eV. (E_photon - KE_max)

But I am not able to figure out a formula for determining the photocurrent.
Thanks.

 

[Mola]

I have found the magic formula from someone. It's power divided by the Energy of the photon, and then multiplying that answer by e(charge of an electron). I ended up getting 9.1mA.