An ideal Carnot heat engine operates on a temperature difference of $210$ degrees. One third of the heat absorbed from the source is discharged to the sink. If the work done per cycle is $400\; J.$ The amount of heat absorbed $(q_2)$ by an engine at source is _________

Question

$(a)\;600\;J \\(b)\; - 600 \;J\\(c)\;300\;J \\(d)\;-300\;J$