Prepare / Execute Method Error

I'm having problems passing in variables into my execute statement. Any
ideas?

*
*

**

*Table:*
CREATE TABLE cat.case
(
vari character varying(50), --Contains Value
‘BDD1’
ht numeric(4,1) --Contains
Value 30.0
)

*Statements:*
PREPARE insert_plan (character varying, numeric) AS
SELECT vari FROM cat.case WHERE vari = $1 AND ht = $2;

EXECUTE insert_plan(*vari_string*, *case[1]*); *--Fails with Errors
vari_string* = 'BDD1' --character varying
*case[1]* = 30.0 --numeric(4,1)[]

*Errors:*
NOTICE: vari_string: BDD1 NOTICE: ht: 30.0
ERROR: function insert_plan(character varying, numeric) does not exist
LINE 1: SELECT insert_plan( $1 , $2 [ $3 ])
HINT: No function matches the given name and argument types. You might need
to add explicit type casts.
QUERY: SELECT insert_plan( $1 , $2 [ $3 ])

*Hard Coded – It will work! It just doesn’t like using variables inside???*
EXECUTE insert_plan('BDD1', 30.0);

*Another Variation of the Execution Statement and still failed.*
EXECUTE insert_plan(vari_string:: character varying(50), case[1]::
numeric(4,1));