Section 94H. There shall be maintained at all times in the hands of the attorney in fact, or trustees duly authorized for that purpose, assets in cash or securities equal to all outstanding claims and liabilities, including a reserve liability on contracts in force, that is premium reserve, calculated on the same basis as for mutual companies transacting the same kinds of business, except that during the provisional certifying period specified in section ninety-four D, said premium reserve shall be prorated to an amount commensurate with the number of contracts held and claims outstanding. There shall also be maintained as a surplus any additional sum necessary to meet the standards of solvency required of mutual companies transacting the same kinds of business which, in the case of exchanges, shall in no event be less than two hundred thousand dollars. Such surplus shall, in the case of a domestic exchange, be in cash or invested according to the laws applicable to the investment of the surplus of mutual companies transacting the same kinds of business. The attorney in fact or the subscribers may make deposits to maintain the surplus at the required amount, which shall be made upon condition that they shall not be repaid to the depositor until such time as repayment thereof will not reduce the surplus below the required amount. Exchanges shall be subject to section five, section twenty-three A and section one hundred and fifty-six A.