Trigger adjustment

[gyt]

Hi everyone.
Can somebody help me with this?
I have 389 Lakelander rifle and the trigger pull is heavy(1.5 kg).
I enclose photo of the trigger. Is there a way to reduce trigger pull?
With what screws?(b,c)What is the minimum trigger pull?
https://picasaweb.google.com/102295141220273634712/July32012#slideshow/5760840993280636482
Thank you
Ringman