Assume a PL/I program that wants to execute a call to an external procedure. This procedure expects 1 parameter and returns 1 parameter. Which instructions do you have to provide in the main program? (1) DCL MYSUB ENTRY (CHAR(5)) EXTERNAL; (2) DCL MYSUB ENTRY (CHAR(5)) RETURNS (CHAR(5)) EXTERNAL; (3) DCL MYPARAMETER,MYRESULT CHAR(5); (4) CALL MYSUB (MYPARAMETER); (5) MYRESULT = MYSUB; (6) MYRESULT = MYSUB(MYPARAMETER);