A, B, and C used Ruyi cards on their mobile phones, and received a discount of one month's basic call charges. All three of them exceeded the basic call charges. As a result, A paid 70 yuan, B paid 50 yuan, and C paid 30 yuan. The total length of the three-person call is 90 hours. If these times are used by one person, they need to pay 350 yuan. How many more hours does A compare with C this month?
甲、乙、丙三人的手机动用了如意卡，并获得了赠送一个月基础通话费的优惠，三人均超过了基础话费，结果甲支付了70元，乙支付了50元，丙支付了30元，三人通话总长为90小时，如果这些时间由一个人通话使用，需要支付350元，那么本月甲比丙多通话多少小时？
<gadget id="calculator">70 + 50 + 30</gadget>
<output>150</output>

<gadget id="calculator">350 - 150</gadget>
<output>200</output>

<gadget id="calculator">200 / 2</gadget>
<output>100</output>

<gadget id="calculator">100 + 70</gadget>
<output>170</output>

<gadget id="calculator">100 + 50</gadget>
<output>150</output>

<gadget id="calculator">100 + 30</gadget>
<output>130</output>

<gadget id="calculator">170 + 150 + 130</gadget>
<output>450</output>

<gadget id="calculator">170 / 450</gadget>
<output>17/45 = around 0.377778</output>

<gadget id="calculator">130 / 450</gadget>
<output>13/45 = around 0.288889</output>

<gadget id="calculator">(17/45) - (13/45)</gadget>
<output>4/45 = around 0.088889</output>

<gadget id="calculator">90 * (4/45)</gadget>
<output>8</output>

<result>8</result>