A letter to the author of the calculations in the White-Hall Evening-Post relating to South-Sea stock. Shewing The mistakes in the said calculations; and, These being Rectified, What the Present Value of South-Sea stock is. Together with An answer to the Unjust Insinuations against the Estimate of the Value of South-Sea Stock, lately Published, as if that Treatise were intended to prejudice the Unhappy Sufferers, who have dealt in South-Sea Stock, or to hurt the Publick Credit. By a Member of the House of Commons