There shall be charged in respect of the duties of the Official Trustee such fees, whether byway of percentage or otherwise, as the Government may prescribe. 1* * * * *

The fees under this section may be at different rates for different properties or classes of properties or for different duties, and shall, so far as may be, be arranged so as to produce an amount sufficient to discharge the salaries and all other expenses incidental to the working of this Act (including such sum as Government may determine to be required to insure 2* the Government 3* against loss under this Act).