I been trying to do this question and it is causing me a lot of stress. Any1 have any ideas???

Circle C has centre (5,-1). the line L: 3x-4y+11=0 is a tangent to C.
(i) Show that the radius of C is 6.
(ii) The line x+py+1=0 is also a tangent to C.Find two possible values for p.

I can do part (i) its (ii) that I cant get to work out.

thanks to anyone who helps...