Four program modules form part of a program for a library. A description of the relationship between the modules is summarised as follows: Module name | Description --- | --- UpdateLoan() | • Calls either LoanExtend() or LoanReturn() LoanExtend() | • Called with parameters LoanID and BookID | • Calls CheckReserve() to see whether the book has been reserved for another library user | • Returns TRUE if the loan has been extended, otherwise returns FALSE CheckReserve() | • Called with BookID | • Returns TRUE if the book has been reserved, otherwise returns FALSE LoanReturn() | • Called with parameters LoanID and BookID | • Returns a REAL (which is the value of the fine to be paid in the case of an overdue loan)