A wholesaler purchased electric goods for the taxable amount of Rs. 1,50,000. He sold it to the retailer for the taxable amount of Rs.1,80,000. Retailer sold it to the customer for the taxable amount of Rs.2,20,000. Rate of GST is 18%. Show the computation of GST in tax invoices of sales. Also find the payable CGST and payable SGST for wholesaler and retailer.