3. Show the stack with all activation record instances (with all fields), when execution reaches position 1 in the following skeletal program. Assume bigsub is at level 1. 15 pts function bigsub() { var bigl1; function a(flag, ap1) { var al1; function b() { var bl1, bl2; ... a(false, bl2); ... } // end of b ... if (flag) b(); else c(ap1, al1); ... } // end of a function c(cp1, cp2) { function d(dp1, dp2) { var dl1; ... <------------------------1 } // end of d ... d(cp1, cp2); } // end of c ... a(true, bigl1); ... } // end of bigsub The calling sequence for this program for execution to reach d is bigsub calls a a calls b b calls a a calls c c calls d