Calculate the element of this total amount of tax which relates to the second lease by applying the fraction:
Cyfrifo elfen y cyfanswm hwn o dreth sy’n berthnasol i’r ail les drwy ddefnyddio’r ffracsiwn: GNP2 ÷ CGNP gyda chyfanswm y dreth sydd i’w godi ar y CGNP