Microsoft Corp yesterday set the basic monthly charge for the Microsoft Network at $4.95, and that includes three free hours a month; the extra-time charge is $2.50 an hour. The company is also offering annual membership and a frequent-user plan, both at discounts on the basic monthly rate. The Charter Member Annual Plan is limited to the first 500,000 customers, and is $39.95 a year with three hours’ free usage per month; each additional hour is $2.50. Thereafter the Annual Plan is $49.95 per year with three hours of free usage per month with each additional hour at $2.50. The Frequent User Monthly Plan is $19.95 monthly for 20 hours of usage a month with each extra hour at $2. The Standard Monthly Plan is $4.95 monthly and includes three hours of usage per month; each extra hour is $2.50. Microsoft will also offer a trial period on the service at no charge for 30 days or 10 hours, whichever comes first. Membership provides full Internet access, including an electronic mail account, thousands of newsgroups, and World Wide Web access.The service will also carry hundreds of independent content providers charging for their services.