Find AC in the diagram below
[asy]
size(140);
pair A,B,C,O;
A=(-cot(5pi/12),0);
B=(cot(pi/4),0);
C=(0,1);
draw(A--B--C--cycle);
dot("$A$",A,SW);
dot("$B$",B,SE);
dot("$C$",C,N);
label("$75^\circ$",A,2dir(32));
label("$45^\circ$",B,3dir(155));
label("$30$",A--B,S);
[/asy]
