MODEL:
! A model of a home mortgage(WHATIF.LNG);
! The user is prompted for values for the
  payment, years, and interest rate.  The
  face value of the mortgage (LUMP) is 
  solved for.;
 DATA:
! User is prompted for these:;
   PAYMENT  = ?; ! Monthly payment;
   YEARS    = ?; ! No. of years;
   YRATE    = ?; ! Interest rate;
 ENDDATA

! Relate no. of months to no. of years;
   MONTHS = YEARS * 12;

! Relate monthly interest rate to yearly rate;
   ( 1 + MRATE) ^ 12  =  1 + YRATE;

! Relate lump sum to monthly payment, monthly
  interest rate, and no. of months;
   LUMP = PAYMENT * @FPA( MRATE, MONTHS);

END