pipe a fills a tank of capacity 700 liters at the rate of 40 liters a minute. another pipe b fills the same tank at the rate of 30 liters a minute. a pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. if pipe a is kept open for a minute and then closed and pipe b is open for a minute and then closed and then pipe c is open for a minute and then closed and the cycle is repeated, when will the tank be full?  Choose the correct choice: A) 42 minutes B) 14 minutes C) 39 minutes D) 40 minutes 20 seconds E) none of these
<gadget id="calculator">40 + 30</gadget>
<output>70</output>

<gadget id="calculator">70 - 20</gadget>
<output>50</output>

<gadget id="calculator">700 / 50</gadget>
<output>14</output>

<gadget id="calculator">14 * 3</gadget>
<output>42</output>

<result>A</result>
pipe a fills a tank of capacity 700 liters at the rate of 40 liters a minute. another pipe b fills the same tank at the rate of 30 liters a minute. a pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. if pipe a is kept open for a minute and then closed and pipe b is open for a minute and then closed and then pipe c is open for a minute and then closed and the cycle is repeated, when will the tank be full?
multiply(divide(700, subtract(add(40, 30), 20)), const_3)
"in one cycle they fill 40 + 30 - 20 = 50 liters 700 = 50 * n = > n = 14 here n = number of cycles . total time = 14 * 3 = 42 as in one cycle there are 3 minutes . thus 42 minutes answer : a"