(a)in the case of an insurer not carrying on solely re-insurance, business, one--fourth of one per cent of the total gross premium written direct in India in that class of insurance business during the year preceding the year in which the application for renewal of registration is required to be made by insurer (the amount of fee so arrived at, if not an integral number of rupees, being rounded off to the next lower integral rupee), or five hundred rupees, whichever is greater;