a,the cost of a call includes a 3.99dollar connection fee plues 3.99 dollar per minute,so the function rule for the cost of a call is y=3.99+3.99x (dollar) b.a 10-minute in-flight call cost y=3.99+3.99*10=43.89（dollar）
英文的数学题,请将每一步用英文解释清楚
a,the cost of a call includes a 3.99dollar connection fee plues 3.99 dollar per minute,so the function rule for the cost of a call is y=3.99+3.99x (dollar) b.a 10-minute in-flight call cost y=3.99+3.99*10=43.89（dollar）