Section 16
SEC. 16. The rates charged by the grantee, its successors or assigns shall be subject to regulation by the Public Utility Commission, and the right is hereby reserved to the Government of the Philippine Islands to regulate the rates to be charged by the grantee, its successors or assigns, but any rates which shall be fixed shall be sufficient to yield a reasonable return to the grantee, its successors or assigns, upon the capital invested after making due allowance for maintenance, operation and other necessary expenses.