Newbie here.  I'm trying to run a scheme program from gsi and getting an error I don't understand:

C:\gambit\gambitv4.6.2\v4.6.2\bin>type timecalc.sch
(define hrs1)
(define hrs2)
(display "Hrs 1: ") (set! hrs1 (read))
(display "\nHrs 2: ") (set! hrs2 (read))

(print "\n\n" (+ hrs1 hrs2) " hours --> $" (* (+ hrs1 hrs2) 22))'

C:\gambit\gambitv4.6.2\v4.6.2\bin>gsi -:d0 timecalc.sch

C:\gambit\gambitv4.6.2\v4.6.2\bin>gsi timecalc.sch
*** ERROR IN "timecalc.sch"@7.1 -- Datum expected

C:\gambit\gambitv4.6.2\v4.6.2\bin>gsi
Gambit v4.6.2

> (load "timecalc.sch")
*** ERROR IN "timecalc.sch"@7.1 -- Datum expected
1>

Any tips?

TIA, Steve