3.9.4 All monthly recurring charges are billed one month in advance. Initial and final month's billing, when the service period is less than a month, will be prorated at l/30th of the month's recurring charge for each day the service was rendered or equipment was provided.

3.9.5 Usage charges are billed monthly for the preceding billing period. For periods less than the monthly billing period, minimum usage charges are prorated at l/30th of the monthly minimum amount for each day the service was rendered.

3.9.6 The duration of a call is rated in intervals of the billing increments described for each service provided in this price list. If the final interval of a call is less than the applicable billing increment, it will be rounded up to a full increment for purposes of billing.

3.9.7 Computed usage charges or credits for each call are rounded to the nearest cent when possible.

3.9.8 The applicable usage rates for the billing of a distance sensitive call will depend on the distance in airline mileage between the originating and terminating points of the call. For the purpose of determining the airline mileage of a call, the Company will utilize the vertical ("V") and horizontal ("H") coordinates of the rate centers of the originating and terminating points of the call. For purposes of billing, the Company references "V" and "H" coordinates provided by Bell Communications Research. Calls originated by dialing a local exchange number or a 950-type number using an authorization code, the originating point will be the rate center in which the switched access facilities are located. For calls originated via equal access connections, WATS access lines or dedicated access lines, the originating point will be the rate center in which the Customer is located. The terminating point will be determined by the rate center of the called number.

The formula to determine airline miles is as follows:

(((V1 - V2) ^ 2) + ((H1 - H2) ^ 2)) / 10

3.9.9 Unless noted otherwise, applicable rate periods, as indicated below, are based on the time in which a call is established. In cases where a call begins in one rate period and continues into another, the rate in effect in each period will apply to the portion of the call occurring within the applicable rate period.