The following table shows four points from a monthly longdistance telephone billing plan. Longdistance Bill ($/month) Total Longdistance Calls (min/month) 20 10 30 20 40 30 50 40 If all points of the billing plan are on a straight line: 0 Find the vertical intercept of the corresponding equation without graphing it. 0 What is the monthly xed fee? What is the charge per minute? 0 How much would the charges be for 1~hour long'distance calls per month