What should be the fees?

I have 3 very small proprietory firms in Mumbai each with turnover of 2 to 2.5 lacs.

In each firm the total invoices are 30 - 40 per year.

Even purchase entries are very very less

Firms are GST registered

What should be the CA fees for a year for
1) Accounts, GST compliance and filing and
2) Income Tax return filing with P&L, Balance Sheet and Computation of Income.

Thanks in advance.