MySQL Stored Procedure Case Statement Syntax Error - Contd

The Procedure contains syntax error. Please help me in finding the error. The mySQL Workbench says that this has 8 errors and this cannot be applied to the database. I have already posted this question. People told me to change the CASE statement to IF.Even after changes, the error persists. I don't know how to nest this post under the original question. The actual post was posted in this link. Revised syntax is posted as requested @Caius Jard

CREATE PROCEDURE `calculate_amount` (in IN_book_id INT,  in IN_qty INT )
BEGIN
-- declare
DECLARE m_prdct VARCHAR(10);
DECLARE m_cust_id INT(5);

-- select into
SELECT 
    Product
FROM
    Bookings
WHERE
    Book_id = IN_book_id INTO m_prdct;

SELECT 
    Cust_id
FROM
    Bookings
WHERE
    Book_id = IN_book_id INTO m_cust_id;

-- conditionals & action
IF (m_prdct = '20ltr') THEN
INSERT INTO Amount(Cust_id,Book_id,Can,300ml,500ml,1lit,2lit) VALUES(m_cust_id,IN_book_id,(SELECT Rate.Can*Bookings.Qty FROM Rate,Bookings WHERE Bookings.Book_id=IN_book_id),0,0,0,0); 

ELSEIF (m_prdct = '300ml') THEN
INSERT INTO Amount(Cust_id,Book_id,Can,300ml,500ml,1lit,2lit) VALUES(m_cust_id,IN_book_id,0,(SELECT Rate.300ml*Bookings.Qty FROM Rate,Bookings WHERE Bookings.Book_id=IN_book_id),0,0,0);

ELSEIF (m_prdct = '500ml') THEN 
INSERT INTO Amount(Cust_id,Book_id,Can,300ml,500ml,1lit,2lit) VALUES(m_cust_id,IN_book_id,0,0,(SELECT Rate.500ml*Bookings.Qty FROM Rate,Bookings WHERE Bookings.Book_id=IN_book_id),0,0); 

ELSEIF (m_prdct = '1ltr') THEN 
INSERT INTO Amount(Cust_id,Book_id,Can,300ml,500ml,1lit,2lit) VALUES(m_cust_id,IN_book_id,0,0,0,(SELECT Rate.1lit*Bookings.Qty FROM Rate,Bookings WHERE Bookings.Book_id=IN_book_id),0); 

ELSE 
INSERT INTO Amount(Cust_id,Book_id,Can,300ml,500ml,1lit,2lit) VALUES(m_cust_id,IN_book_id,0,0,0,0,(SELECT Rate.2lit*Bookings.Qty FROM Rate,Bookings WHERE Bookings.Book_id=IN_book_id)); 
-- end
END IF;
END