a man purchased earphone on friday.but he forgot how much it cost.the data he have are mean expenditure of all 7 days is 500.expenditure on mon,tue,wed,thurs,sat,sun are 450,600,400,500,550,300.on friday he purchased three things one earphone,one pen and one notebook.pen cost 30 and notebook cost 50.then what is cost of earphone?	Pick one:	A) 620	B) 530	C) 450	D) 470	E) 500
solution   let expenditure on Friday be x   (450+600+400+500+x+550+300)/7=500   2800+x=3500   x=700   pen+notebook+earphone=700   earphone=700-80= 
<gadget id="calculator">700-80</gadget>
<output>620</output>
620   answer 620
<result>A</result>
a man purchased earphone on friday.but he forgot how much it cost.the data he have are mean expenditure of all 7 days is 500.expenditure on mon,tue,wed,thurs,sat,sun are 450,600,400,500,550,300.on friday he purchased three things one earphone,one pen and one notebook.pen cost 30 and notebook cost 50.then what is cost of earphone?