Help with LINGO $20\mathrm{.}0?$ need a syntax intervention

I am writing a code for my pet recycling model

$/*$ Sets $*/$

set Customers $/$ a$1,$ a$2,...,$ an$/$;

set X$1$s $/$ b$1,$ b$2,...,$ bm$/$;

set X$2$s $/$ c$1,$ c$2,...,$ cn$/$;

set QualityLevels $/$ d$1,$ d$2,...,$ dq$/$;

set ProductVarieties $/$ f$1,$ f$2,...,$ fp$/$;

$/*$ Parameters $*/$

param FCb; $/*$ Fixed cost of X$1*/$

param Qb$($b$)$; $/*$ Capacity of X$1($b$)*/$

param Dc$($i$,$ b$)$; $/*$ Distance from X$2($i$)$ to X$1($b$)*/$

$...($other parameters$)$

$/*$ Decision Variables $*/$

var BinaryVar$\_$CustToX$1($a$,$ b$),$ in $0,1$; $/*$ Customer a assigned to X$1$ b$?*/$

var BinaryVar$\_$X$1$ToX$2($b$,$ c$),$ in $0,1$; $/*$ X$1$ b assigned to X$2$ c$?*/$

$...($other decision variables$)$

$/*$ Objective Function $($Minimize Total Cost$)*/$

min TotalCost:

sum$($a in Customers, b in X$1$s$)$ FCb $*$ BinaryVar$\_$CustToX$1($a$,$ b$)+$

$...($other cost components from all phases$)$;

$/*$ Constraints $*/$

$...($Constraints for customer assignment, capacity, balanced allocation, routes$)$