Points $A$, $B$, and $C$ are on sides $\overline{WX}$, $\overline{YZ}$, and $\overline{XY}$ of rectangle $WXYZ$ as shown below such that $XA = 4$, $YB = 18$, $\angle ACB= 90^\circ$, and $YC = 2XC$. Find $AB$. [asy] pair A,B,C,D,P,Q,R; A = (0,0); P = (0,0.7); B = (0,1); R = (0.4,1); C = (1,1); Q = (1,0.2); D = (1,0); draw(P--B--C--D--A--P--R--Q--P); draw(rightanglemark(P,R,Q,2)); label("$W$", A, SW); label("$Z$",D,SE); label("$X$",B,NW); label("$Y$",C,NE); label("$C$",R,N); label("$A$",P,W); label("$B$",Q,E); label("$4$", (B+P)/2,W); label("$18$", (C+Q)/2,E); [/asy]
Sorry if the latex is hard to read
